ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 67 



sea-urchins and Holothurians with the external medium are semi- 

 permeable, as are also the walls of the water-vascular system, the polian 

 vesicles, and the digestive tubes of Holothurians. 



Ccelentera. 



Development of Corymorpha.* — Albert J. May undertook the study 

 of Corymorpha pendida with special reference to the development of the 

 medusoid, and to the origin of the sex cells. His results may be 

 summarised thus : — Corymorpha is a solitary form, developed from a bud 

 of the peduncle wall, in which the attaching filaments and papilla? are 

 modifications of the same structure. The central axis of the stem is 

 filled with parenchyma-like cells in which extensions of the hydranth 

 cavity are found as longitudinal canals. Owing to the development of 

 gland cells in the hydranth cavity, digestion and circulation have become 

 localised. The sex cells are derived from an apical plug of ectodermal 

 cells, and in the case of the ova, the development is by absorption of the 

 germinal tissue, thus giving rise to a syncytium in which the nuclei of 

 the primitive germ cells persist for a time. 



Depastrum.| — E. S. Russell contributes a few notes on the rare 

 Lucernarid Depastrum cyathiforme (Gosse). Its peculiarly local distribu- 

 tion is difficult to account for, but he has found that it never occurs iii 

 muddy localities, nor in spots where there is much decaying sea-weed. 

 He shows that instead of there being many rows of tentacles, as Haeckel 

 says, there are only two. He found two types, one with a long narrow 

 umbrella and the other with the umbrella as broad as long. His paper is 

 of interest as a record of the fairly abundant occurrence of a Lucernarid 

 around the Cumbraes, etc., which is but little known to the majority of 

 British zoologists. 



Porifera. 



Haddonella.J— Igerna B. J. Sollas gives an account of the new genus 

 Hadclonella, a ceratose sponge belonging to the Dendroceratina, paying 

 special attention to the structure and development of the pithed fibres of 

 Haddonella topsenli. She finds that Haddonella and Ianthella are closely 

 allied in having cells in the cortex of their pithed fibres. The growing 

 points consist of naked pith secreted by a many-layered cap of spongo- 

 blasts. Layer after layer of spongoblasts deposit spongin until finally 

 the pith is enclosed in many successive sheaths of spongin, between 

 which lie the spongoblasts, which have diminished and lost their granular 

 contents. These results justify Polejaeff's assertion that the presence of 

 cells in the spongin of sponge-fibres is a character of sub-family or 

 family value. 



Protozoa. 



Nuclear Apparatus in Paramcecium.§ — P. Mitrophanow has studied 

 the functions and accompanying changes of structure in the nuclei of 

 Paramecium. The micronucleus plays the principal part in the pheno- 

 mena of multiplication and conjugation ; it exhibits the principal 



* Araer. Nat.. 1903, pp. 579-99 (12 figs.). 



t Ann. Nat. Hist. xiii. pp. 62-5 (1 pi.). 



\ Op. cit, xii. (1903) pp. 557-63 (2 pis.). 



§ Arch. Zool. Exp., 1903. pp. 411-35. 



F 2 



