50 SUMMARY OF CURRENT RESEARCHES RELATING TO 



from its parent, but the basal attachment sh'ghtly modifies the process. 

 The fragment cut off curls together until its extremities meet, making 

 parts of mesenteries before nearly parallel now radial in arrangement, 

 thus attaining the sea-anemone structure with the least expenditure of 

 energy. 



Development of Cunina proboscidea.* — J. Stschelkanowzew has 

 been able to work out the development of this Medusa. It seems 

 likely that its life-history is complicated by the occurrence of two 

 distinct generations. The one leads a parasitic life, complicated by the 

 budding of its larval stage and the consequent formation of colonies. 

 From the ova of the Medusa which are produced l)y these colonies, 

 the second rudimentary generation develops (in their eiidoderm and 

 gastro-vaseular cavity), and eventually infects Carmarina hastata. 



Hydra orientalis.t — Nelson Annandale describes this new species of 

 Hydra from Bengal. It is related to H. grisea, which it resembles in 

 the structure of its normal egg. The number of tentacles differs at 

 different seasons in different generations. C^omparatively few buds are 

 produced. Vertictil fission occasionally occurs. The species is dioecious. 

 A rise in temperature induces a proportion of the individuals in an 

 aquarium or a pond to develop testes ; if considerable, it may induce a 

 few of those tliat remain to produce eggs. As a result of exhaustion 

 eggs are sometimes produced which do not secrete a horny outer shell. 

 Individuals are short-lived and perish after sexual reproduction, several 

 generations l;jing completed in a year. 



The Indian species is more delicate than the European forms. It is 

 far from plastic to changed conditions, and heat is most inimical to its 

 life. It moves away from light, probably because it is repelled by heat. 

 It progresses chiefly by crawling. The colour is due to solid particles in 

 the endoderm derived from the food, and in unfavourable conditions 

 the polyp may lose its colour. 



Bionomical Relations of Hydra orientalis.| — Nelson Annandale 

 notes that unicellular Algai settle on the surface of Hydra orientalis — 

 this might be the beginning of symbiosis. What seems to be Vorticella 

 monUiita was found attached in groups to the body of the polyp. The 

 polyp is not infrequently attached to the shell of Paludina, which is 

 undoubtedly useful to the Hydra. A chironomid larva feeds on Hydra 

 orientalis. The oriental Hydra feeds in the early morning — on Cladocera, 

 Copepoda, Rotifers, minute Oligochseta, and insect larvse. 



Budding and Sexual Reproduction in Hydra fusca.§ — Richard 

 Hertwig has made a careful study of this fresh-water polyp. It is 

 distinctly male or female. A distinction between a stalk and a pigmented 

 body is very marked. There is a definite rhythm in the budding. The 

 buds appear one above the other at regular distances. This depends on 

 nutritive conditions. The similarity between the early stages of buds 



* MT. Zool. Stat. Neapel, xvii. (1906) pp. 433-86 (2 pis.), 

 t Mem. Asiatic Soc. Bengal, i. No. 16 (1906) pp. 339-59, 

 J Journ. Asiatic Soc. Bengal, ii. (1906) pp. 109-16. 

 § Biol. Centralbl., xxvi. (1906) pp. 489-508. 



