VOL. LXXVII.] PHILOSOPHICAL TRANSACTIONS. 34/ 



The crystalline humor resembles that of the quadruped; but whether it is 

 very convex or flattened, I cannot determine, those I have examined having 

 been kept too long to preserve their exact shape and size. The vitreous humor 

 adhered to the retina at the entrance of the optic nerve. The optic nerve is 

 very long in some species, owing to the vast width of the head. I shall not at 

 present consider the eye in animals of this tribe, as it respects the power of 

 vision, that being performed on a general principle common to every animal in- 

 habiting the water; more especially as I am only master of the construction and 

 formation of the eye, and not of the size, shape, and densities of the humors; 

 yet from reasoning we must suppose them to correspond with the shape of the 

 eye, and the medium through which the light is to pass. 



Of the parts of generation. — ^The parts of generation in both sexes of this 

 order of animals come nearer in form to those of the ruminating than of any 

 others; and this similarity is perhaps more remarkable in the female than in the 

 male ; for their situation in the male must vary on account of external form, as 

 was before observed. The testicles retain the situation in which they were formed, 

 as in those quadrupeds in which they never come down into the scrotum. They 

 are situated near the lower part of the abdomen, one on each side, on the 2 

 great depressors of the tail. At this part of the abdomen, the testicles come in 

 contact with the abdominal muscles anteriorly. The vasa deferentia pass di- 

 rectly from the epididymis behind the bladder, or between it and the rectum, into 

 the urethra; and there are no bags similar to those called vesiculae seminales in 

 certain other animals. 



The structure of the penis is nearly the same in them all, and formed much 

 on the principle of the quadruped. It is made up of 2 crura, uniting into one 

 corpus cavernosum, and the corpus spongiosum seems first to enter the corpus 

 cavernosum. In the porpoise at least the urethra is found nearly in the centre of 

 the corpus cavernosum; but towards the glans seems to separate or emerge from 

 it, and becoming a distinct spongy body, runs along its under surface, as in 

 quadrupeds. The corpus cavernosum in some is broader from the upper part to 

 the lower than from side to side ; but in the porpoise has the appearance of being 

 round, becoming smaller forwards, so as to terminate almost in a point some 

 distance from the end of the penis. The glans does not spread out as in many 

 quadrupeds, but seems to be merely a plexus of veins covering the anterior end 

 of the penis, yet is extended a good way farther on, and is in some no more 

 than one vein deep. 



Tiie cura penis are attached to 1 bones, which are nearly in the same situa- 

 tion, and in the same part of the pelvis, as those to which the penis is attached 

 in quadrupeds; but these bones are only for the insertion of the crura, and not 

 for the support of any other part, like the pelvis in those animals which have 



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