210 THE GENERAL ANATOMY OF GORILLA [SECT. A 



measured 51 mm. by 26 mm. The tunica vaginalis bounded a 

 closed sac. No hydatids were seen. The epididymis was placed 

 as in Man but on its dorsal aspect a large accumulation of fatty 

 tissue was noticed. 



Professor Retzius very kindly reported on the two testes 

 described above. That of the Gorilla was imperfectly preserved, 

 but the testis of the Chimpanzee provided well-preserved sperm- 

 cells. The characters of these are mentioned in the following 

 paragraphs. 



The spermatozoa of the Gorilla have been described by Professor 

 Retzius 1 , who has illustrated his admirable observations in several 

 well-known memoirs. 



The sperm-cells possess distinctive features in each of the 

 larger Simiidae, and while the Orang-utan is quite aberrant in 

 these respects, the Chimpanzee and the Gorilla must be placed 

 much closer to Man in regard to such characters. 



(a) In the spermatozoa of the Gorilla (Fig. 143, No. 7) the 

 head is of ovoid form, though flattened in one plane : when 

 viewed in the flattened aspect, the acrosome (perforatorium) is 

 seen to be more slender towards its free extremity than in the 

 Chimpanzee. In this respect the Gorilla is of all the Primates 

 the form most similar to Man. 



(b) The pars conjunctionis of the tail (with the included 

 centrosomes) is relatively shorter in the Gorilla than in the other 

 Simiidae, and herein again the human conditions are most nearly 

 approached by the Gorilla. (It may be added that a small New- 

 World monkey, viz. Callithrix, and the Hylobates resemble Man 

 and the Gorilla in this detail.) 



(c) The pars principalis of the tail is (in the sperm-cell of the 

 Gorilla) slender and of moderate length. Again the Gorilla makes 

 the closest approach to the condition found in Man. 



This survey of the main characters of the Simiidae shews then- 

 close similarity to the Hominidae : at the same time differences as 

 well as resemblances are indicated, differences chiefly noticeable in 

 two connections, viz. with the adaptation of Man to the erect 

 attitude, and sec* dully, with the concomitant development of brain- 



1 Retzius, Biologische Untersuchungm, N.F. B<1. xvn. 1912 and Anat. Anz. 1913. 



