202 NOTES AND MEMORANDA. 



primitive layers, consists of oval cells much crowded together. 

 In the peduncle two nucleated cells make their appearance, the 

 rudiments of the pedal gland. 



Stage 4. Very slight changes except in size. The three 

 layers are enlarged. The two cells representing the pedal 

 gland become pyriform, and the longitudinal fissure is elon- 

 gated. 



The author here notes that the ectoderm and endoderm of the 

 bud are the product of the ectoderm or integument of the parent, 

 a point upon which Vogt also insists. 



He then proceeds to follow the development of the different 

 internal organs, the further modification of the form of the bud 

 itself being unimportant. 



Stage 5. According to Nitsche and Oscar Schmidt, the cavity 

 of the digestive tube is formed early. In L. crassicauda the 

 rudiment of this organ is a completely solid body, viz. the compact 

 mass of endodermal cells already mentioned. Vogt also describes 

 the stomach as at first perfectly solid. 



The differentiation of the rudimentary digestive canal com- 

 mences by the formation of a cavity at the top of the bud, imme- 

 diately below the longitudinal fissure in the ectoderm previously 

 noted. This primitive hollow is due, the author thinks, to the 

 atrophy of some of the endodermal cells. It gives origni to the 

 cavity of the digestive canal and to the intratentacular space (the 

 Vestibule). 



I am quite unable to harmonise the account given by the 

 author of this portion of the developmental history with that 

 which we have from Vogt.i 



Stage 6. The rudimentary digestive canal takes on the form 

 of a cul-de-sac, in which two regions are distinguishable — the 

 upper, which is broad and furnished with thick walls and 

 represents the Vestibule, and the lower, which is bent backwards, 

 and is the rudiment of the digestive tube and the rectum. The 

 summit of the bud is already obliquely truncated, a character 

 which is distinctive of the genus. 



A small oval body is now visible, placed in the fold or bend of 

 the digestive tube, and probably derived from the endoderm. The 

 author considers it to be the rudiment of the nervous ganglion. 

 At this stage, too, some cells are distinguishable on the surface 

 of the stomach, which from analogy he thinks may be the rudir 

 ments of the sexual organs. Their origin he was unable to 

 determine. 



Stage 7. The bud has increased considerably in size. The 

 rudiments of the tentacles are apparent as minute prominences on 



1 Vide the October No. of this Jourual, page 369. 



