347 



is seen on the liguie, along and close to the lateral surface of the 

 gland, almost straight downwards to the genital »orifice« of the third 

 pair of legs. It is possible that von Ihering has also seen traces of 

 these ducts as he says : « II m'a paru qu'un conduit très délicat se 

 dirigeait plus en avant, à l'ouverture du 3ème coxopodite, mais 

 je ne puis l'affirmer. « Both ducts are however, in their upper parts, 

 of nearly the same size and it was rather easier to find the anterior 

 ones. But the ducts to the fifth pair of legs become gradually a good 

 deal stouter when they have entered the upper part of the leg which 

 portions of the ducts correspond to the ductus ejaculatorius. Their 

 width is however on my material never more than about 1 mm and 

 hardly that much. The situation of the origin of the anterior ducts 

 is similar to that where the vasa deferentia of the common crayfish 

 begin. The question might therefore arise whether both pairs are able 

 to act as spermducts. This could however hardly be discerned on 

 this material without sections, and hardly anyway if the constitution 

 of the genital »orifices« did not give the answer (see below). 



In the females (see Fig. 2) the ducts of the anterior pair are much 

 larger. They take their origin at the upper lateral surface of the ovary, 

 close to the angle between the 



vertical and horizontal portion '^' " 



of the gland, and lead from 

 there almost straight down to 

 the orifices on the third coxo- 

 podites. These are, of course, 

 identical with the oviducts of 

 the common crayfish, and in 

 one of the examined speci- 

 mens I have seen an egg enter- 

 ing the upper part of these ducts , so there can be no doubts whatever 

 with regard to its function. The ducts of the posterior pair begin 

 laterally and not far from the posterior end of the ovary, as can 

 be seen on the figure. They are much smaller than the anterior 

 ducts and much too narrow to allow the passage of an egg. Thus 

 they cannot act as oviducts, but are only rudiments. But it is of 

 importance to let the genital »orifices« undergo a closer examination. 

 It has been said above, that there are two pairs of genital orifices, 

 namely on the third and fifth pairs of legs and it really seems to be 

 so. If we now fust select a male specimen we find the genital orifices 

 on the coxopodites of the fifth pair of legs situated on prominent warts 

 and about them there can be no doubt that they really are openings. 



But the »orifices« on the third pair of legs, which at first seem to 



25* 



