lit)"' ExcretoTy Organs in Bdellostoma Stouti 



was liad to tlio spinal ganglia for the pnrpose of determining relative 

 positions. It now sooms best to employ the myotomes for this purpose, 

 especially since in the earlier embryos there is an intimate relation 

 between the myotomes and the excretory organs. It has been found 

 that the first spinal ganglion is located between the third and fourth 

 myotomes, so that where trouble is experienced in counting the myo- 

 tomes, the ganglia may be counted instead, and the necessary calculations 

 made. 



The anterior end of the excretory system is more or less rudimentary, 

 and the position of the first tubule is not constant, but varies both in 

 different individuals and on the two sides in the same individual. In a 

 few cases where its position could be accurately determined, and where 

 there w^as no probability of degeneration having taken place, it occurred 

 in segments eleven to thirteen. In one of the specimens previously 

 studied the first tubule occurred in sections passing through the sixth 

 ganglion. But here the preservation is not all that could be desired, 

 and it is possible, though not certain, that this may really be the seventh 

 ganglion, and the tubule might correspond to the myotome just back of 

 this, which would be the tenth. But making all possible allowances, 

 the fact remains that here the first tubule is farther forward than in 

 any other embryo studied. 



The position of the posterior end of the segmental duct has been found 

 to vary from about the seventy-ninth to the eighty-second segment, and 

 possibly a larger nmnber of specimens would show still greater variation. 



In. general it may be said that in this animal there is a good deal 

 of variation, l:)oth in the embrj^o and in the adult, a fact that should 

 not be lost sight of in attempting to generalize from a small number 

 of individuals. 



So far as my knowledge extends Dean ' is the only other person who 

 has published observations on the excretory system in. the embryos of 

 Bdellostoma. From surface views alone he has described a series of 

 segmental structures, about eighty in number, extending from the region 

 of the neck into that of the tail, and present for a comparatively long 

 period of the development. They are described and figured as large and 

 somewhat complicated bodies, each extending outwards from near the 

 spinal ganglion to the distal region of the somite, and it is suggested 

 that they may be tubules of a pronephric nature. In sections of embryos 



^ Dean, Bashford: On the Embryology of Bdellostoma stouti. A General 

 Account of Myxinold Development from the Egg and Segmentation to Hatch- 

 ing. Festschrift zum siebenzigsten Geburstag von Carl von Kupffer. .Tena, 

 1899. 



