ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 175 



Howe Island and similar localities. The collection is of great scientific 

 interest, not merely because eighteen of the species have not hitherto 

 been described, but also because of the new light which it throws on the 

 breeding habits of some species and the distribution of certain geneni. 

 A new genus of Ophiuroids, named Astrorhombus, has the disc covered 

 by a very irregular, rough pavement of granules and plates of very 

 diverse sizes, without any definite indication cf radial shields. 



Coelentera. 



Nervous System of Hydra.* — Jovan Hadzi describes nerve-cells, 

 processes of nerve-cells, sensory nerve-cells, and sensory cells. The 

 greater part of the system is an ectodermic network. It is not 

 appropriate to speak of neurons, for the cells are directly connected by 

 plasmic processes, and Hydra is too far away from the type in reference 

 to which the concept of neurons was established. The author has also 

 studied the reactions of Hydra to contact stimuli, corroborating on the 

 whole the results of previous investigators. 



Oogenesis of Hydra.f — Elliot R. Downing gives an account based 

 partly on his own observations and partly on those of others. In H. 

 dicecia the ovaries are large and contain several ova ; H. viridis, H.fusca, 

 and H. yrisea have one or very rarely two. The ovary is formed by rapid 

 mitosis of interstitial cells beside the egg or eggs. There is no evidence 

 of a migration of interstitial cells into the ovary. The interstitial cells 

 form radiating rows to facilitate the transfer of nutritive material to 

 the ova and to carry away the excretory products. The egg-cell is dis- 

 tinct from the interstitial cells from the start. The changes in shape, 

 in granulation, in the size and structure of the nucleus, and so on, are 

 described. The " pseudo-cells " are nuclei of ingested interstitial cells 

 or are due to a confluence of small yolk-granules formed by the egg. 

 When their formation is complete, the pseudopodia of the egg-cell are 

 withdrawn. The first polar spindle has twelve chromosomes and the 

 second six. 



On the whole one is impressed, in a study of the ovogenesis of the 

 Hydra, with the independence of the egg and its antagonism to the parent 

 organism ; it ingests portions of it as a parasite might live on a host. 

 From the first the egg-cell pursues its destined life-history : it grows 

 and matures, going through a definite cycle of events, dependent on the 

 adult Hydra only for food. If constancy in the nucleo-plasma relation 

 is characteristic of the life-cycle of the soma (and that seems very doubtful) 

 it certainly is not for the germ-cells ; on the contrary, continuous change 

 seems to mark this relation in their life-cycle. 



Budding and Shoot-formation of Hydroids.J — Alfred Kuhn has 

 made a fresh study of the hydroid colony. He shows that the mode of 

 budding is much more diverse than is usually supposed. He illustrates 

 convergence, e.g. in parallelisms between Hydrallmania and Aglaophenia 

 types, and maintains that the selectionist interpretation is applicable to 



• Arbeit. Zool. Inst. Univ. Wien, xvii. (1909) pp. 225-68 (2 pis. and 2 figs.). 

 t Zool. Jahrb., xxviii. (1909) pp. 296-324 (2 pis. and 2 figs.), 

 j Tom. cit., pp. 387-476 (6 pis. and 22 figs.). 



