ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 325 



no morphological structure. The very large nuclei of these cells can be 

 followed until the beginning of the pharyngeal invagination. The yolk 

 in these cells breaks up into spherules, probably through the action of 

 enzymes from the large nuclei. This liquefied yolk is afterwards absorbed 

 by the endoderm cells. 



A large portion of the ectoderm is formed by the successive budding 

 or delimination of small cells from larger, deeper-lying cells. A portion 

 of the mesoderm, chiefly that part lying around the pharynx, is de- 

 rived from cells of the second quartet, and thus corresponds to 

 the ' ; secondary " mesoblast or " larval " mesenchyme of Annelids and 

 Molluscs. 



In the spiral cleavage, the segregation of the ectoblast in three 

 quartets, the formation of a large part of the mesoderm from 4 d, the 

 formation of the apical cells, and in many other details, the development 

 corresponds to that of Annelids and Molluscs. On the other hand, in 

 the development of the entire alimentary canal from a portion of the 

 mesentoblast, 4 d, and in the consequent degeneration of the " macro- 

 meres " and of the remaining cells of the fourth quartet, this Polyclad 

 is unique. 



Nematocysts of Turbellaria.*— C. H. Martin has experimentally 

 proved in a series of Turbellaria that their nematocysts are derived from 

 their food. For example, if Microstoma lineare is fed upon Gordylo- 

 pltora, the nematocysts of this polyp are found under its skin. Ordi- 

 narily its nematocysts are derived from Hydra, upon which it feeds. 

 The same process probably occurs in the other Turbellaria, with the 

 possible exception of Anonymus virilis, and therefore there is no ground 

 for the generally accepted homology between nematocysts and rhabdites. 



Rotifera. 



New French Rotifers.f — P. de Beauchamp describes Proalides 

 te/itaculatas g. et sp. n., a remarkable footless Notommatid adapted for 

 free-swimming. It has affinities with Proales, Taphrocampa, and possibly 

 Adadyla. The author also describes Proales similis sp. n. and Rattulus 

 cylindricus Imhof, var. chattoni var. n. 



New Scottish Rotifers.} — James Murray, in a supplementary note 

 on Scottish Rotifers collected by the Lake Survey, gives lists of species 

 found, mostly in moss, in various parts of North Scotland, Orkney and 

 Shetland. Amongst these are the following new species : Philodina 

 convertjens, CaUidina minuta, C. circinata, C. plicata var. hirundella, 

 which are described and figured. 



'&■ 



Stomachal Excretion in Rotifera.§ — P. de Beauchamp describes a 

 process observed in the stomach of Rotifera in which a selective action 

 is exercised whereby from amongst the substances swallowed, e.g. 



* Quart. Joum. Micr. Sci., lii. (1908) pp. 261-77 (1 pi.). 



t Bull. Soc. Zool. France, xxxii. (1907) pp. 148-57 (3 figs.). 



I Trans. Roy. Soc. Edinburgh, xlvi. (1908) pp. 189-201 (2 pis.). 



§ Comptes Rendus, cxliv. (1907) pp. 1293-5. 



