579 



" On the Chorda dorsalis," and two supplementary memoirs " On 

 the Corpuscles of the Blood." The volume of the Transactions 

 for 1842 -contains his memoir "On Fibre," and that for 1843 his 

 capital discovery of the " Spermatozoa found within the Ovum." 



These Researches in Embryology contain a comprehensive, well- 

 selected and well-conducted series of original experiments and obser- 

 vations on the formation and earlier stages of development of the 

 ovum in the Rabbit and Dog, and in examples of the oviparous verte- 

 brate classes from the bird to the fish. In the first series the author 

 determined the order of formation of the different parts of the ovum, 

 and the nature and mode of development of the vesicle called 

 1 ovisac,' in which those processes take place. He made known the 

 nature and traced the development of the so-called " disc of Von 

 Baer," and detected in it a peculiar mechanism (retinacula) which 

 he supposed mainly to regulate the transit of the ovum into the 

 Fallopian tube. In the second series Dr. Barry traced the 

 changes which the ovum undergoes in its passage through the Fal- 

 lopian tube ; the earliest and most interesting stages of mammalian 

 development being for the first time described in this memoir. The 

 important discovery of the segmentation of the yelk of the mamma- 

 lian ovum is communicated in this memoir (1839), in which he first 

 extended to that class the observation of a phenomenon which had 

 previously been known only in the Batrachia. Dr. Barry's discovery 

 made on the ovum of the Rabbit, was subsequently confirmed by 

 Prof. Bischoff, in the ovum of the Dog and Guinea- pig. 



Another most important observation, communicated by Dr. Barry 

 to the Royal Society, in his Third Series, 1840, of the penetration 

 by the spermatozoon of the ovum in the Rabbit, by an aperture in 

 the zona pellucida, was of so minute and difficult a kind that it did 

 not at once command assent. In 1843, Dr. Barry, however, pub- 

 lished a confirmatory observation, which he had then made, of 

 spermatozoa within the ovum of the Rabbit, taken from the Fallo- 

 pian tube and in process of segmentation. 



These statements at first met with positive denial by Professor 

 Bischoff, who had failed in his attempts to repeat Dr. Barry's obser- 

 vations : and it was not until nine years afterwards that the observa- 

 tions of Dr. Nelson, on the impregnation of the Ascaris mystax*, 



* Philosophical Transactions, 1851. 



