REPORT ON THE PYCNOGONIDA. 



103 



nuclei, in these cavities. This was in the first tibial joint of the leg of Colossendeis 

 leptorhynchus ; however, I think there can be no doubt that these same cells will also be 

 found in the other joints of the legs of this species. Each cell terminates in a long and 

 slender appendage, which probably extends to within a small space of the opening of the 

 canal. Most probably these are the glands which, according to Dohrn, are always present 

 in these integumentary cavities. I have figured these glands in fig. 1 of Plate XVIII. ; { is a 

 part of the wall of the intestinal csecum, which runs through the joint ; c, c are parts of the 

 septa of connective tissue, which seem to form here separate chambers in connection with 

 the difierent cavities. These chambers contain numerous blood-corpuscles of an irregular 

 spool form, and towards the pore-canal are furnished with two {cl), in an other cavity 

 three {d') glandular cells, with very large nuclei. The specimen, the integument of 

 which shows these glands, is a female. 



Returning to these integumentary cavities, and their ordinary, viz., their respiratory, 

 function, I have stiU to mention that I found them in many species with many blood- 

 corpuscles in their interior, and that often also a nerve is seen which sends a very thin 

 branch into them. These I observed more accurately in Colossendeis 23'>'oboscidea, Sab. 

 (See later, under peripheral part of the nervous system.) 



The number of these cavities is different in the diff"erent species. I counted them in 

 transverse sections of the fourth joint of the leg in some fourteen species, belonging to 

 five genera, and compared them with the girth of the joint. This I did to ascertain if 

 there was any relation between the number of these cavities and the depth at which the 

 species lives. That such a relation does not exist, and that the greater or smaller number 

 of these cavities is one of the properties of the natural groups (genera) of the Pycnogonids, 

 is shown, I believe, hj the following table : — 



