386 s. HATTA : 



with the aorta " {loco cit., p. 213). The glomerulus figured in 

 his Taf. 17, fig. 12 {(jl) corresponds, I think, with a part of the 

 ü'lomerulus in Petrorniizony 



As is very well known, the independent studies of Weiss 

 ('00) and Boveri ('02) on tlie branchial chamber of Amphioxus 

 gave a new direction to the morphological investigation of this 

 field. A number of external openings of ciliated tubes is found 

 at the dorsal corner of the peribranchial chamber of Amphioxus. 

 Through the morphological study and physiological experiments 

 this organ-system is demonstrated to be the excretory apparatus, 

 or " Nierencanälchen," as Boveri calls them, of Amphioxus. 



Boveri counted 01 "Nierencanälchen" in an individual 4 cm. 

 in length and possessing 183 gill-bars on the right side. In the 

 adult he counted about 180 of the '' Nierencanälchen "; the number 

 is, however, by no means constant, but varies within a certain limit. 



In the middle region of the branchial chaml^er, a " Nieren- 

 canälchen " has 3 or 4 " Seitentrichter," and 2 " Endtrichter ;" 

 such is the most complete one. It becomes gradually simplified 

 both anteriorly and posteriorly, until it is at last represented by a 

 short single tubule, as seen in Taf. 33, figs. and 13, given by 

 Boveri. The tubules in the anterior and posterior part of the 

 system thus show a sign of degeneration, as in the case of the 

 pronephros of Cyclostomata. 



1) Dkan has published two ijapers on the development of the Californian Hag ('98 and 

 '99) ; these excellent works contain merely the general account of the course of the develop- 

 ment in surface view- VVe may expect that tlie full account will throw much light on the 

 ontogeny of Craniota. There stand, in the account given by him in these works, the im- 

 portant facts that the " pronephric tubules are apparent in connection with all the meso- 

 blastic somites" ('93, p- 274) and that the pronephros is extended far backwards, beyond the 

 anal region, into the tail ('99, p. 27-)- It would be liighly desirable to observe the pronephric 

 tubules of the Hag in relation tu the myomere, and not to the spinal ganghia alone, as PracE 

 has done. 



