60 ART. 4. N. YATSU : 



band appears to have been mistaken by Brooks for a nervous 

 element ('78 PL II., Fig. 3, and PI. III., Fig. 6). Blochmaxn 

 ('00) is of the same opinion as myself, stating clearly the absence 

 of a nerve ring around the oesophagus (p. 124.). 



In connection with the mesenteries I shall describe the 

 primary germ-cells. In the 8 p. c. stage I was able to detect 

 what are supposed to be the germ-cells. They, though few in 

 number (PI. VIL, Fig. 107, gm. cl.), form part of the epithelial 

 cells which constitute the ileo-parietal band. These cells greatly 

 exceed their fellows in size : the nucleus is vesicular with a single 

 well dinned nucleolus, and the cytoplasm is highly granular. 

 They greatly resemble the germ-cells of young Lingula in position 

 as well as in cytological features. 



*. Nephridia. 



Blochmann ('98 and '00) considers the otocysts described 

 by Fritz Müller ('60) and Brooks ('78) as the nephridia, but 

 these vesicles, as far as my observations go, have been rightly 

 interpreted by the earlier writers. I may here refer to a pair of 

 string-like organs which I discovered in the larva? of Lingula: 

 structures which I do not hesitate to consider as the Anlagen of 

 nephridia. They certainly answer all the conditions of an ex- 

 cretory organ — moreover there are no other organs in the adult 

 which appear to be developed out of them, if we except the 

 nephridia. The reasons given on the following pages, I believe, 

 will be found adequate to justify my determination of the string- 

 like organs. It is indeed remarkable that so conspicuous an organ 

 as the structure in question should have entirely escaped observa- 

 tion by former writers. 



