594 A. WILLET. 



cells which lie upon the membrana limitans of the aorta. 

 These latter cells are identified as soleuocytes^ since each of 

 them gives off peripherally a long and delicate tubule, which 

 passes straight across the lumeu of the nephridium to the 

 opposite wall, where it penetrates between the cells of the 

 cubical epithelium. The solenocytes occur along the entire 

 dorsal wall of the orgau, and all the tubules converge towards 

 the orifice, from which numerous fine long flagella depend 

 into the preeoral gut; these are the flagella of the solenocytes. 

 Goldschmidt therefore defines Hatschek's nephridium as a 

 portion of the coelom constricted from the left head-cavity 

 (which gives rise to the prteoral pit or prteoral organ), and 

 effecting a communication with the pra3oral gutby a pronephric 



Fig. 6. — Diagram of Hatscliek's nephridium, showing solenocytes 

 and the orifice into the prseoral gut. After Goldschmidt. 



canal. It thus appears that Hatschek's nephridium has a 

 structure analogous to that of Boveri's tubules as corrected 

 by Goodrich. 



Dr. G-oldschmidt has found no other excretory tubes in 

 Amphioxides, but describes some structures which he calls 

 " Schwammkorper " occurring segmentally on the left side at 

 the dorsal recess of the body- cavity in the region of transition 

 between pharynx and intestine ; they appear as a f eltwork or 

 mass of spongy tissue with nuclei and solenocyte tubules.^ 



Noteworthy features in the vascular system of Amphi- 

 oxides are the absence of a portal system, the presence of 

 an unpaired aorta, and especially the fact that the branchial 

 artery, which is a direct continuation of the sub-iutcstinal 



' Possibly they have some relation to Lankestcr's brown funnels (sec also 

 Burehardt, 'Jena Zeitschr.,' 1900). 



