NOTES AND MEMORANDA. 201 



unite in a common stem, which opens on the side of the body 

 by an extremely minute orifice. The author conjectures thae 

 these structures may be excretory organs — renal glands. Ht 

 then proceeds to give an elaborate account of the gemmation, as 

 observed in L. crassicauda. 



He first notes the fact that buds are formed upon the pri- 

 mary buds before their separation from the parent, and points 

 out that in tliese secondary buds the earliest stages of the 

 development are most readily studied. I shall give a very 

 brief outline of the process of development as he has reported 

 it. 



The buds in this species are produced on the ventral surface 

 of the body, and are placed symmetrically on each side of the 

 longitudinal axis of the cup. 



First nuliment of ihe bud, a circle composed of a group of 

 cells in which two cellular layers are distinguishable, one peri- 

 pheric, the other central ; the first made up of many cells and 

 equivalent to the ectoderm ; the second of a single cell, after- 

 wards multiplying by division, and constituting tlie endoderm. 

 These layers are the representatives of the germinal leaves of other 

 animals. 



In this account of the primitive contents of the bud the 

 author agrees with Nitsche, and differs from Vogt, who holds 

 that they are not cellular, but consist of an " undivided sarcodic 

 mass." 



I shall notice the principal divergences between these observers, 

 in order to direct attention to points requiring further investi- 

 gation. 



Stage '1} Endoderm composed of two cells resulting from 

 division of the primitive cell. 



Stage 3. Development of a third layer, the mesoderm, and of 

 the rudiments of certain organs. The form of the whole bud is 

 modified. It now appears as an oval body borne on a short 

 peduncle, a direct continuation of the ectoderm of the parent. 

 Two regions are distinguishable, an anterior and a posterior, the 

 first corresponding to the part on which the crown of tentacles is 

 developed, the second to the stem. A slight longitudinal fissure 

 in the ectoderm on the anterior part, the rudiment of the orifice 

 leading into the intra-tentacular space (the Vestibule). The 

 endoderm and ectoderm are also modified. The cells of the 

 former multiply and it increases in bulk. It is now situated 

 in the anterior portion of the bud, and adheres firmly to the 

 ectoderm, a significant change with reference to the formation of 

 the hood and the digestive tube. The mesoderm, between the two 



* The stages correspond to the figures by which the course of develop- 

 ment is illustrated. 



