478 Mr. J. H. Orton. Occurrence of Protandric [June 8, 



Relation of Primary to Secondary Sexual Characters. 



Having established the fact that a completely continuous series in the 

 reduction of the penis, and correlated increase in size of the uterus occurs, it 

 became clear that continuity of the primary sexual characters should also be 

 found. Accordingly, an investigation was made with this object in view, by 

 means of serial sections of the gonad. 



The gonad in all forms consists of two or three main tubes extending the whole 

 length of the visceral mass, giving off tubular diverticula, which anteriorly divide and 

 subdivide to form a loose compound tubular gland, but which posteriorly divide at 

 most a few times, or are mere blind cseca. The cells lining the tubes proliferate, and 

 some are shed into the lumina as germ cells — eggs or sperms. 



In the male the main tubes of the gonad open into a vas deferens, from a dilatation of 

 which a narrow tube leads to a groove on the dorsal surface of the body. This groove runs 

 towards the head from the anterior end of the visceral sac to the base of the penis, and 

 is continuous with a groove in the latter. In the female the main tubes of the gonad 

 open into the oviduct. A receptaculum seminis opening into the oviduct has been 

 described (3). The relation of the gonad to the gonaducts in the § forms is being 

 investigated. The colour of the gonad in the g is brownish red, that of the § brownish 

 red or orange, occasionally yellow near the uterus, that of the 9 yellow. 



Sections of the ^ forms were naturally cut first, but an examination of 

 the gonad in all those investigated revealed nothing but ova. Sections of the 

 " proximal " males were then prepared, with the result that both ova and 

 sperms were found in the gonad. An examination of the gonad of all the 

 males in a chain indicates, as far as observations go, that there is a gradual 

 increase in ova in the gonad the nearer a male is to the most distal $ ; but 

 even the smallest 's examined have a few ova in their gonad.* It therefore 

 seems doubtful whether pure males, i.e. males with only sperm in the gonad, 

 are ever found in Crepiditla fomicata. Hence the necessity of defining the 

 term " male." The term " male " is usually applied to an organism which 

 produces only sperm in its gonad. As, however, in most of the higher 

 animals a special part of the body is modified into an intromittent organ, the 

 presence of such an organ is adopted as a criterion of maleness. Usually this 

 is a fair inference. In species presenting no sexual dimorphism, such as 

 Amphioxus and Echinoderms, one resorts to the true criterion of maleness or 

 femaleness, namely the production of ova or sperms in the gonad. In 

 Crepid.ula fomicata, therefore, to be strictly accurate one should examine the 

 gonad of every individual possessing even a well developed penis before 

 committing oneself as to its sexual character. As a matter of convenience, 



* Since G. Smith (4) has found ova in the gonad of the $ 's of many species of 

 Crustacea, it would seem that a careful microscopic examination of the gonads of all 

 males, made in the light of these observations, might bring out important facts bearing 

 on the nature of maleness. 



