294 M. E. Claparedc on the Theonj of the 



taking place, the chorion is ft)niied^ and the egg continues ad- 

 vancing by degrees towards the period of its segmentation and the 

 formation of the embryo. The action produced upon the ovum 

 by the spermatozoids is consequently, according to the Glasgow 

 physiologist, of a triple nature : — 1. A preservative action, inas- 

 much as they prevent the destruction and disappearance of the 

 vitelline granules, and their indiscriminate mixture with the 

 elements of the germinal vesicle and spot, which, according to 

 him, inevitably takes place when the ova are not fecundated; 

 2. A destructive solvent action, in consequence of which the 

 vitelline granules and germinal vesicle are gi'adually dissolved at 

 the expiration of a certain time ; and 3. A transforming action 

 by which the vitelline granules are metamorphosed into em- 

 bryonic granules. 



It was reserved for a third English philosopher to assist in the 

 formation of the new edifice, by the announcement of the entrance 

 of the spermatozoid into the ovum in a third class of animals, 

 namely the Reptiles. Newport* in his first memoir on the re- 

 production of the Batrachia, had referred to various experiments 

 which he had made with the view of throwing discredit upon the 

 opinion that the spermatozoids could penetrate into the ovum, 

 which he regarded as possessing but little probability. But a 

 year-and-a-half afterv\'ardst he recalled his previous opinion in a 

 remarkable memoir, in which he stated that he had positively 

 seen spermatozoids, not only within the outer membranes of the 

 ovum of the Frog, but actually in immediate contact with the 

 vitelline membrane. The spermatozoids had their heads always 

 directed towards the centre of the ovum and their tails towards 

 its periphery, as though they wished to penetrate still further. 

 The first consequence of the fecundation thus effected, consists, 

 according to Newport, in the formation of a chamber between 

 the vitellus and the vitelline membrane at one extremity of the 

 egg, and the segmentation of the yelk then commences. In a 

 note written subsequently to the communication of his paper to 

 the Royal Society J, Newport announces that he had actually 

 observed the passage of the spermatozoids through the mem- 

 branes of the ovum and their arrival in the interior of the 

 vitellus. He remarks that the penetration does not take place 

 through a particular opening, but through any point of the sur- 

 face of the chorion. " The spermatozoa," he says, " do not reach 

 the yelk of the Frog's egg by any special orifice or canal in the 

 envelopes, but pierce the substance of the envelopes at any part 

 with which they may happen to come into contact." 



* Phil. Trans. 1851. t Phil. Traus. 1853, part 2. 



X Phil. Trans. 1853, part 2. p. 271 {note). 



