of the Fishery Board for Scotland. 



301 



environment in which a reversion to the primitive type of hermaphrodism 

 is a necessity to the well-being of the organism. Hence, in any list of 

 hermaphrodite animals, if inclusive, some will fall under the former 

 category, such, perhaps, as certain sponges, — turbellaria, sagitta, myxine, 

 &c. (the parasitic or commensal habit of the last has yet to be proved) ; 

 whilst others, with isolated environment, &c, will come under the latter 

 category. The most obvious of this latter class are selected to form a 

 general list of hermaphrodite animals by Pilseneer, and doubtless as 

 many could be selected from the former class to prove that herma- 

 phroditism is a primitive state. To sum up on this point : though it may 

 be shown in Mollusca, Pisces, or other groups, that certain members may 

 revert to the ancestral hermaphrodite condition, yet this does not 

 warrant our assuming that this reversion is a case of evolution de novo 

 of the hermaphrodite condition from a primitive and general unisexuality. 



The occasional occurrence, then, of cases similar to those described in 

 this paper, are to be regarded as atavistic reversions to a primitive condi- 

 tion, occurring more abundantly in the groups in which adaptations are 

 most numerous and the sexual organs are hypertrophied, and in some few 

 cases being intensified and made permanent (tierranus, &c.) features 

 under the action of natural selection. 



Granting, however, that the occurrence of hermaphroditism predominates 

 in the Teleostei and Anura, one may regard the fact as being correlated in 

 its origin with the great diversity of form and shape assumed by the 

 many species of these two successful and progressive branches of the 

 Vertebrata. 



In conclusion, I wish to thank Professor M'Intosh and Dr Fulton for 

 the opportunity of examining these specimens, and Mr T. R. Cansh, of 

 this University, for kind help with the foreign literature. 



