252 J. T. CUNNINGHAM. 



no external opening in this somite; at the angle between the 

 septum behind somite iv and the body wall is a very obvious 

 uephrostome, which ought to lead into the longitudinal tube, 

 into that part of it corresponding to somite v, but the connec- 

 tion could not be traced. Nephrostomes were also present 

 attached to the anterior face of the septa behind somites n 

 and in (the first and second branchiferous), and leading into 

 tubes seen in somites in and iv, but I could find no external 

 openings in these somites. I could find no nephrostome in 

 somite i (the buccal), nor any trace of a tube in somite n. 

 Gonads are present in the form of clumps of deeply-staining, 

 small, indifferent cells, attached to the exterior of all the 

 nephrostoma mentioned, seven in all (see fig. 13). The 

 germinal cells, when still quite undifferentiated, separate from 

 the gonads, and undergo further development in the coelom. 

 But I found no reproductive elements in the cavity of the 

 nephridial system, though the body cavity contained them in 

 quantity, and it is probable that at the right season they are 

 expelled through the nephridial cavities. The body cavity 

 contains, besides the reproductive elements, a large number of 

 spherical, vacuolated, nucleated cells. This is the only case in 

 which a communication between successive nephridia has ever 

 been discovered in any adult invertebrate. It is true that in 

 the development of Polygordius, according to Hatschek, each 

 nephridium gives off backwards a prolongation of itself, from 

 which the next nephridium is formed, and the two remain in 

 communication for a time ; but the connection is soon severed, 

 and in the adult the successive nephridia are isolated and 

 independent. In L an ice conchilega the nephridia have 

 coalesced together after coming in contact from before back- 

 wards, the separating membranes having disappeared. The 

 case is extremely interesting in the fact that we have in it an 

 approximation to the condition of the excretory system in 

 Vertebrata; the presence of a metameric series of nephro- 

 stomata in vertebrate embryos has long ago been seen to 

 constitute a resemblance between them and Chsetopoda, but 

 no other Chaetopod is known which resembles the verte- 



