and Sexual Conditions in certain Isopoda. 417 



Oniscinese {Porcelh'o, Platyarthrus) . In Platyarthrus it 

 appears to be altogether devoid of an excretory duct. A 

 distinct terminal saccule can with difficulty be made out. 

 The gland, which is greatly pressed towards the ventral side, 

 consists of a curved and relatively simple sac, of which the 

 epithelial wall — just as in the Hygrophileje — represents a 

 syncitium. In the plasma two well-marked layers can be 

 distinguished. The lower one, in which also lie the nuclei, 

 is finely granular ; that which clothes the lumen is clear and 

 finely striated. 



Besides urinary deposits in the fat-body, as has been 

 described by Weber in Trichoniscus, we find in Oniscodeae 

 peculiar excretory organs lying in the last three thoracic and 

 in the three to five abdominal segments. In the fourth 

 segment there lies to the side of the abdominal ganglion a 

 large gland, which opens upon the fifth segment (really almost 

 intersegraentally between the fourth and fifth segments). 

 This glandular sac, which in forms provided with pigment is 

 surrounded by a pigmented sheath of connective tissue, is 

 formed for the most part of large cells, and its broad lumen 

 is filled with a finely granular secretion. The organ appears 

 to be of ectodermal origin. 



The glands of the two following segments are thin-walled 

 sacs lying in the region of the lateral blood-lacunae, and their 

 epithelium consists of well-difierentiated cells. The lumen 

 of these glands is filled with a secretion similar to that of the 

 gland of the fourth segment. In respect of these organs the 

 Hygrophileas differ from the Oniscinese in that in the former 

 the two pairs of glands alluded to lie freely in the connective 

 tissue, without efferent ducts and surrounded by lateral blood- 

 lacunaj. In Oniscineai a fine efferent duct runs from the 

 usually irregularly lobed glands, and opens beneath the 

 epimerite in front of the legs of the sixth and seventh 

 segments. In Hygrophileas, however, the glands take the 

 shape of closed sacs, the interior of which is entirely filled 

 with a homogeneous yellowish secretion. The phylogeny of 

 these organs appears to me to be determined by the conditions 

 found in Eaployhtlialmus^ where, besides the large segmental 

 sacs, we meet with small saccules precisely similar to the 

 large ones and lying irregularly distributed in the connective 

 tissue in the region of the blood-lacunge. 



This appears to me to be the original condition of the organs 

 in question. In the connective tissue were deposited — as 

 happens in an intracellular manner in the pericardial tissue — 

 intercellular urinary substances, certain of which developed 

 into large sacs, which finally were enable I to discharge their 



