HEEMAPHRODITE GENITALIA OE THE CODEISH. 557 



uriuo-geuital system. The Dipuoi appear to occupy a partially 

 central position in the collective series ; and while the Marsipo- 

 branchii are undoubtedly referable to a much lower stock than 

 all other living Chordata with the exception of Amphioxus and 

 the Tunicata, their living representatives would appear to have 

 suifered the loss of their genital ducts. The facts concerning 

 them, as I have endeavoured to interpret them, point to an 

 apterygial* Chondrichthyan witli hermaphrodite duct bearing 

 genitalia as, to my mind, the most logically conceivable ancestor of 

 the living Vertebrata. 



I claim for my hypothesis, — i., a not inconsiderable foundation 

 in fact J ii., that it enables us to harmonize the facts of mor- 

 phology of the genitalia of Vertebrates (and especially those of the 

 OsteicTitliyes so long considered anomalous), at least as satis- 

 factorily as any other yet postulated. It renders explicable the 

 absence of vestiges of the ducts of the opposite sexes in the 

 Osteichthyes and Myxichthyes, in that they would appear to have 

 never been formed; and it furnishes at least a possible explana- 

 tion of the constantly recurring reversion of the Teleostean 

 genital glands to an hermaphroditic type. 



EXPLANATION OF PLATE XIV. 



Fig. 1. Genital glands of an hermaphrodite Codfish (Gadus morrkua) ; with 



remains of genital duct, urocyst, and suspensory ligaments. Yenti-al 



aspect. One half natural size. 

 Fig. 2. The same ; head of right ovary with testis-duct, laid open to show their 



interior and details of communication. Natural size. 

 Fig. .3. Salmo salar, 5 Dissection to show the interior of the urino-genital 



sinus, and relations, to the sanie, of the urinary and genital orifices. 



After Carus and Otto (ref. see p. 553). 

 Fig. 4. Salmo salar, (^ . Comparison dissection to fig. 3. After Carus and 



Otto. 



* I would suggest tliis term to express the absence of paired fins, a.s dis- 

 tinguished from the apodal condition in which the pelvic members are alone 

 wanting. 



