EMBRYO: WEEK 1 - Summary

Introduced the idea that there is a joint of two kinds of semen that causes generation, the male’s ejaculate and the female’s menstrual blood. He also supports preformation.

Hippocrates

Published De generatione animalium. Described 2 major patterns of cell division during early development: holoblastic cleavage and meroblastic. Also described the 3 ways animals give birth: oviparity. Viviparity, and ovoviviparity. Supports epigenesis, believing that the organs of an embryo develops gradually and are not preformed. Believes that only the male’s semen, ‘seed’, contributes to the formation of the fetus. 

Aristotle

Supported the idea of Hippocrates. Believed that both seeds of male and female are relevant for procreation. Had a misconception that a female genitalia is just an inverted version of the male’s.

Galen

Contributed to the development of embryology through his artistic anatomical studies. Illustrated how a fetus is formed inside the human uterus through observing a pregnant bicornuate uterus.

Leonardo da Vinci

Supported epigenesis. Published the 1st major publications on comparative embryology, de formato foetu. His publications included illustrations of embryos and fetuses at different stages. A student of Gabriele Fallopio. Bursa fabricius (site of B lymphocyte formation in birds), now known as the cloacal bursa, was named after him.

Hieronymus Fabricius

Described the uterine tubes, formerly known as the Fallopian tube. He also supports epigenesis.

Gabriele Fallopio

supports epigenesis. Best known for his discovery of blood circulation. Gave the first detailed investigation of embryology, Exercitationes de generatione animalium. Challenged Aristotle’s idea, arguing that it was the egg that was fundamental to generation, not the sperm. He later on concluded that Aristotle was right as he found no semen in the uterus.

William Harvey

Supports preformation. Suggests that the development of an embryo is a mere unfolding of an already mature organism.  His experiments on chick embryos initiated what is considered one of the great debates in embryology.

Marcello Malpighi

supported preformation. Concluded that animals came from eggs of the same species as he studied the generation of insects. After he publicized Historia generalis insectorum, he revolutionized the classifications of insects based on their modes of development which are still in use. 

Jans Swammerdam

Supported the spermist idea (preformation). Known for his exceptional making of microscopes. Published the first depiction of spermatozoa by keenfully observing it under the microscope.  Observed ‘animalcules’ with tails under the microscope from the semen sample which Johannes Ham gave. He later confirmed it by observing his own.  Believes that sperms were ‘seeds’ and females are mere soils from which the seeds are planted.

Antonie van Leeuwenhoek

Believed in the spermist idea (preformation). Suggested that a preformed individual exists in the head of the sperm. He calls it ‘Homunculus’ or the tiny man.

Nicolaas Hartsoeker

Proposed the idea the ‘egg’ in the testicles becomes fertile through ‘seminal vapors’ which reach the eggs form the uterus through the fallopian tube.

Regnier de Graaf

Supported epigenesis. proposed ideas that preempted the genetic theory of inheritance from his study of the inheritance of genetic traits.

Pierre Maupertuis

Supported preformation. He is one of ovism’s greatest champions. suggested that chick embryos must be created at the same time as the yolk and, despite unfertilised eggs also containing yolk, believed that embryo have existed there prior to fertilization.  observed that the yolk appeared to be attached to the embryonic chick’s small intestine. 

Albrecht von Haller

Supported preformation. published Traite d'insectologie. provided support to the ovist theory of generation by presenting the parthenogenesis in aphids which could apparently breed for generations despite the absence of males. he argued that females carry within them an entire future generation in miniature form. He suggested that future generations pre-existed within the germ-cells, as though it was similar to the Russian Matryoshka dolls, having miniature versions inside another. 

Charles Bonnet

supported preformation. His experimentations on frogs provided the 1st hard evidence of the sperm’s importance in reproduction. demonstrated that actual physical contact between the egg and the sperm is necessary for embryo development to occur by placing ‘trousers’ made of taffeta on mae frogs.

Lazzaro Spallanzani

Supported epigenesis. Rejected the theory of preformation and instead revived the theory of epigenesis in his dissertation Theoria generationis during the late 18th century.

Kaspar Friedrich Wolff

Supports epigenesis. His chick embryo studies debunked preformation and introduced induction in organ development. One of 3 pioneers who revolutionized embryology.

Christian Heinrich Pander

Supported epigenesis. Expanded Pander’s idea to all vertebrates, discovering the mammalian egg in 1826. His laws refuted old concepts, emphasizing sequential trait development. His unlabelled 1828 embryos hinted at a shared vertebrate stage. One of 3 pioneers who revolutionized embryology.

Karl Ernst von Baer

Supported epigenesis. explored vertebrate system development, describing R****e’s pouch and detailing structures’ evolution. One of 3 pioneers who revolutionized embryology.

Heinrich Rathke

Validated the claims of sperm formation and its union to the egg by describing sperm formation in adult testes.

Rudolph Albert von Kolliker

Achieved the first successful mammalian embryo transfer by transferring embryos from an Angora rabbit to a foster rabbit of a Belgian line, resulting in the birth of a live offspring. His conclusion, that a uterine foster mother does not influence the breed of her foster children, likening her uterus during gestation to a bed of soil with various nutrient constituents, laid the foundation for modern commercial embryo transfer in cattle.

Walter Heape

Revealed that genes are located on chromosomes, establishing the mechanical foundation of heredity and laying the groundwork for modern genetics.

Thomas Morgan Hunt

Achieved a significant milestone by cloning a frog. Their method involved transplanting blastula nuclei into enucleated eggs, resulting in the development of normal embryos. This marked the first successful nuclear transplantation in Metazoans, although it’s important to note that the transplants utilized undifferentiated nuclei.

Robert Briggs and Thomas Joseph King

Extended the Briggs and King. His seminal 1962 paper described the transplantation of intestinal epithelial cell nuclei from Xenopus tadpoles into enucleated frog eggs, resulting in the development of normal tadpoles. His success revealed a significant conceptual advance in developmental biology.

John Gurdon

Achieved sheep cloning through nuclear transfer using cells from early embryos.

Steen Malte Willadsen

Modified the cloning procedure. Successfully cloned the first mammal with fully differentiated adult mammary cells, Dolly, the Finn Dorset lamb. This groundbreaking achievement demonstrated that the nucleus of an adult mammalian somatic cell could be reprogrammed to develop an entire organism.

Ian Wilmut and Keith Campbell