418 Herr B. N^mec on Excretory Organs 



secretion to tlie exterior by means of an excretory duct of 

 secondary origin. 



In the first three abdominal segments {PorceUio) — in Li- 

 gi'diiwi, in all probability in the two following ones also — •[ 

 found coiled and ramifying canals, which send out efferent 

 ducts towards the bases of the several branchial opercula. 

 The canals in question again are situated in the region of 

 those blood-lacunas in which the blood from the branchiae 

 streams up into the pericardium. If these tubes really 

 function as excretory organs their difference in form and 

 structure from the excretory organs of the last thoracic 

 segments may be explained by the fact that in this case it is 

 oxydized blood that is dealt with, while, on the other hand, 

 the former excretory organs are washed by venous blood. 



In the case of Asellus urinary deposits in the fat-body 

 have already been recognized by Leydig in what are known 

 as Zenker's glands. These glands are distinguishable with 

 the naked eye as being composed of separate globules, each 

 of which represents a single cell, and these cells may attain a 

 size of as much as 8 millim. Their plasma is entirely 

 obliterated by spherical concretions. But these cells still 

 exhibit a large nucleus, provided with nuclear reticulum and 

 chromatin granules, which appears to be for the most part 

 pressed flat and much emarginated. Consequently we are 

 here dealing not with a mechanical deposition of secreted 

 substances, but with a vital energetic activity of certain 

 specified cells of the connective tissue. 



I shall publish elsewhere a detailed description of the 

 sexual organs of Isopods. I will here only allude to certain 

 phenomena w^iich are correlated with hermaphroditism. 



The oviducts in Oniscodete open, as is well known, upon 

 the fifth segment. The distal portion of the oviduct secretes 

 the receptacula seminis, discovered by Schobl, as hollow 

 chitinous structures or as solid styles. It is manifest that 

 this portion is of ectodermal origin, as is also proved by its 

 embryology. Now, I found in males of Platyarthrus in the 

 fifth thoracic segment the same structure which in immature 

 females represents the rudiment of the distal section of the 

 oviduct. This consists of a blind tube projecting into the 

 body-cavity, which in young males is filled with a solid style 

 of chitin, but in older ones with a hollow blind ciiitinous 

 cylinder that is undoubtedly homologous with the female 

 receptaculum. We must regard this as an hermaphrodite 

 structure. As regards internal sexual organs I searched in 

 vain for phenomena which could be connected with the con- 

 dition in question. On the other hand, 1 directed my 



