348 



be very plain, show themselves, when closer examined, to be only 

 sham. They are but shallow grooves the appearance of which agrees 

 very closely -with the usual shape of the genital orifices of the other 

 sex on this place. The chitinous shell is, however just about as firm 

 on this spot as any where else on the coxopodite. Although the male 

 Parastacus has two pairs of genital ducts it has only one pair of true 

 orificies, namely, on the fifth pair of legs. If we now examine a female 

 specimen we see at once the conical warts on the fifth coxopodites 

 but these warts do not show, even under a lens, any opening in the 

 tops neither can any opening be felt with a fine needle. They are 

 sometimes provided with a groove in the top, but even then there seems 

 to be no opening, and even if it was, this must be too small to permit 

 the passage of an egg. On the third coxopodite of the female the 

 genital opening is large and easily seen, but it seems to be closed by 

 comparatively thin chitinous membrane. If we however press that 

 membrane, only a little, it falls back and opens on the median side thus 

 showing itself to be only a valve. The female too has thus only one 

 pair of true genital orifices. I have made sections through the ducts to 

 the third pair of legs of the male, as well as through the ducts to the 

 fifth pair of the female and have found both provided with an open 

 and well limited lumen. The former ducts have thin walls and com- 

 paratively how epithel. The latter have comparatively thick muscular 

 walls showing most plainly circular fibres. The epithel of these «mas- 

 culine ducts« of the female is different in diff"erent parts, in some it is 

 comparatively low, in others it consists of high, cylindrical cells. The 

 cells are always larger in these ducts than in the »feminine ducts« of 

 the male. The state of preservation of my material does not make it 

 advisable to go into further details. It seems, however, as if the structure 

 of these supernumerary ducts was rather similar to that of the nor- 

 mal ones. 



We have now seen that the above mentioned supernumerary ducts 

 really are such, and provided with a lumen, although they cannot have 

 any function because the exterior opening is closed. But Avhat is the 

 condition of the genital glands? Do they show any traces of herma- 

 phroditism? In the females the ovaries contain large reddish looking 

 eggs with mean diameter of 2 mm. They lie densely crowded and do 

 not seem to leave room for anything else but eggs in this organ. But 

 w'hen I have taken of the substance of the testis and macerated the 

 same in glycerine I have seen some comparatively large bodies of a 

 very dense structure, resembling eggs. The same is the case when 

 I have prepared sections through this organ. Here and there I have ne 

 found the same bodies sometimes sinsrlv. sometimes in a small number 



