TRANSACTIONS OP THE SECTIONS. 139 



animals ; but in the Ascaris, this part, in its growth, by thickening from the 

 nucleus, never closes completely over it, but leaves one side as it were open, occu- 

 pied by the remains of the granular covering and by the nucleolus. The develop- 

 ment, accordingly, never reaches that stage, in which, as shown by KoUiker's most 

 recent observations in the higher animals, the caudal filament is formed by pro- 

 longation from the closed nucleus. The want of motion in the spermatozoa of the 

 Ascaris, the author considered to be dependent on the absence of the caudal fila- 

 ment, which, when present, acts precisely in the manner of a vibratile cillum. 



The author entered into various details as to the particulars in which his observa- 

 tions agreed with or differed from those of Reichert, Nelson, Bischoff, and Meissner, 

 on the same subject. 



0)1 the Brain of the Troglodytes niger. 

 Sy Professor Allen Thomson, 31. D,, F.R.S. 



As the brain of the Chimpanzee had been little investigated by anatomists, the 

 author exhibited and described a dissection of it which he had recently had an 

 opportunity of making. The specimen belonged to a female, which was probably 

 of six or seven months old. The author called attention to the various points of 

 resemblance and difference between the human brain and that of the Chimpanzee 

 and other Simise. The communication was illustrated by photographic and other 

 representations, and by dissections of the brains of various animals. 



Contributions to the History of Fecundation in different Animals. 

 By Professor Allen Thomson, M.D., F.R.S. 



In this paper, the author first gave an account of a series of observations which 

 he had made, confirmatory of Dr. Ransom's discovery of the micropyle aperture 

 in the ovum of fishes, viz. in the salmon, trout, and stickleback, and the fact 

 of the entrance of the spermatozoa within the membrane of the ovum. 



The author next gave a detailed description of the development of the ovum in 

 Ascaris mystax ; and in connexion with the mode of its fecundation, adverted par- 

 ticularly to the fact, which he had placed beyond doubt, that at the time when the 

 peculiar motionless spermatic bodies first meet with the ova in their descent 

 through the female passages, and effect fecundation by the peculiar penetration 

 observed by Dr. Nelson, the ova are destitute of any membranous covering; and 

 the spermatozoa come, therefore, into direct contact with the exposed surface of the 

 yolk. Professor Thomson's observations were, therefore, in support of the views 

 of Dr. Nelson on this subject, and in opposition to those of Meissner, who con- 

 ceives that, in Ascaris as in Mermis, the spermatozoa are introduced through 

 a micropyle aperture in a inembranous covering ; and to those of Bischoft', who 

 denies the spermatic nature of the bodies referred to. 



Professor Thomson described an observation in which he had fully confirmed 

 the statement originally made by Dr. Martin Barry, of the penetration of the sper- 

 matozoa into the mamraiferous ovum, as has more recently also been observed by 

 several continental physiologists. The author's observations were made on several 

 ova taken from the Fallonian tube of a rabbit, about seventy hours after sexual 

 intercourse, in all of which he detected very clearly a considerable number of 

 spermatozoa within the zona, but without his being able to peiceive any indication 

 of an aperture or micropyle in that membrane. 



The author next passed in review the various observations of recent authors with 

 regard to the micropyle structure, and the phsenomena of fecundation related to it, 

 or independent of it, in different animals ; more particularly those of J. Muller, 

 Newport, Meissner, Keber, Leuckart, Leydig and others, and deduced some 

 general conclusions therefrom as to the manner of the fecundating process. From 

 these it appeared that the micropyle aperture, first discovered by J. Muller in 

 Holothuria, is of frequent occurrence in the ova of animals ; that it is not invariable, 

 however, but that when present it is always related to fecundation ; that in some 

 animals it exists from the earliest condition of the ovum, while in others it is of 



