ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 755 



Coelenterata. 



Notes on Medusae.* — C. Keller has some observations on Cotij 

 lorliiza tuberculata, whicli appears at certain periods in the Mediter- 

 ranean, and the habits of which invite the question, what are the 

 causes of its regular migration, and whence does it come ? From 

 the series of observations which the author was able to make he 

 was led to conclude that it is highly probable that this Medusa is 

 a true deep-sea form, which only comes to the surface for a time, and 

 spends most of its life in its sessile condition on the floor of the sea. 

 The cause of the migration appears to be associated with reproduc- 

 tion, the nurses being littoral, the young Medusas deep-sea forms, 

 so that the sexually mature animal rises to the surface and lives 

 pelagically. With reference to the theories that may be based upon 

 these facts Keller quotes Carl Vogt, who has lately expressed his 

 belief that the class Hydromedusfe has arisen from two different 

 stocks, one of which has produced the Acraspedota and the Scypho- 

 stomata, the other the Craspedota, Siphonophora, and hydroid polyps, 

 and who, further, has expressed his belief that fixed and parasitic 

 creatures are always produced by special adaptation from forms that 

 were primitively free. Though this, of course, is not true of Comatula, 

 yet we must remember how infinite are the powers of adaptation, and 

 not summarily reject it as not applicable to the Medusae. 



The yellow cells of C. tuberculata are next discussed, and the 

 author declares his agreement with the views of Geddes and of 

 Brandt that the bodies are algar in nature, and thinks that the 

 symbiosis is explicable on the supposition that the cells in question 

 are found only in the pelagic generative forms, which demand a 

 larger supply of oxygen. 



A new Medusa — OrcJiistoma agaraciforme — the first species of the 

 genus found in Europe (Mediterranean), is next described. As the 

 development of the Orchistomidse is as yet altogether unknown, it is 

 interesting to learn that Keller has found some young specimens ; it 

 was found that the gonads are only apparently canular, and that they 

 really arise from a gastric outgrowth, a condition as yet unique 

 among the Thaumantidae or Leptomedus®. There appears to be a 

 considerable amount of metamorphosis ; the most important changes 

 obtaining in the radial canals, which increase in number; in the 

 gastric cavity, which diminishes in size ; and in the proportionately 

 late development of the large gastric stalk. 



Revision of the Madreporaria.t — Prof. P. M. Duncan gives a 

 revision of the families and genera of the Sclerodermic Zoantharia, 

 Ed. & H. or Madreporaria (M. Rugosa excepted). Since Milne- 

 Ed w-ards and Haimes' work of 18 GO, no systematic revision of the 

 Madreporaria has appeared, while since then a great number of new 

 genera have been founded ; hence the necessity for a revision has 

 arisen, and more especially in consequence of the morphological 

 researches of Dana, Agassiz, Verrill, Lacaze-Duthiers, and Moseley. 



* Eecueil Zool. SuiBse, i. (1884) pp. 403-22 (1 pi.). 



t Journ. Linn. Soc. Lond. (Zool,), xviii. (1884) pp. 1-204. 



