408 



jrARGARET KOBINSON, 



Mysis. He believed them to be genital cells^ and found 

 tliem later in the abdomen^ later again in the thorax in a 

 ventral position, and later still in a dorsal position between 

 the digestive canal and the heart. However, he is not very- 

 convincing in this part of his paper, and I am inclined to 



Diagram 2. — Median longitudinal section through embryo at 

 Stage D. Ec. 'Eciodern). E'^ Endoderni. Ji/e*. Mesoderm. Froc. 

 ProctodBeum. SL Stomodfeum. 



think that these large cells, in Nebalia at least, are simply 

 part of a zone of growth similar to the Kuospungs-zone 

 described by Reichenbach. This zone of growth is mentioned 

 by Nusbaum, but has been much more fully described in 

 Mysis by Bergli (1893). As I unfortunately did not notice 

 it while making surface views of the embryos I have been 

 unable owing to want of more material to describe it. 



The Dorsal Organ. — I have not found a trace of a 

 dorsal organ in any of my stages, and in this my account 

 of the development differs from that of Butschiusky 

 (1900). 



