ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 257 



in the region of fusion of these edges. The regenerative development 

 of mesenteries is described in detail. The development of the fertilized 

 ovum has not been followed. The failure to obtain developmental 

 stages, together with the abundance of stages in asexual reproduction, 

 may mean that the latter constitutes ihe chief means of maintaining or 

 rapidly increasing the population of a given region. J. A. T. 



Dorsal Mesenteric Filaments of Siphonozooids of Pennatulacea. — 

 Constance M. Lightbown {Manchester Memoirs, 1916, 62, Xo. 4, 

 1-20, 1 pi.). Mesenteric filaments (dorsal) are present in the genera 

 examined, except in Renilla, throughout the siphonozooids of the more 

 primitive genera — that is, in those genera where autozooids and siphono- 

 zooids occur together on the rachis, or where the autozooids are arranged 

 on very primitive leaves. The dorsal mesenteric filaments have an 

 exhalent function. In Renilla there is a special exhalent zooid, and in 

 the higher genera the mesenteric filaments are similarly supplanted by 

 special zooids. In some cases — e.g. Pennatula grandis and Pteroeides 

 pellucidum — there are special zooids (Hickson's " mesozooids ") and also 

 filaments in the siphonozooids. Throughout the order it may be stated 

 that generally the mesenteric filaments are present in the more fleshy 

 species and absent in the slender forms. J. A. T. 



Note on Cavernularia llitkenii. — J. Stuart Thomson {Manchester 

 Memoirs, 1917, 62, No. 7, 1-5, 2 pis., 1 fig.). Some descriptive notes 

 on this species and a record of its occurrence in the seas, of Natal. It 

 has been previously recorded farther north in the Indian Ocean, and it 

 is well known that the coast of Natal is washed by a warm current from 

 the Indian Ocean. J- A. T. 



Nerve-Conduction in Jellyfish.— Alfred Goldsborough Mayer 

 {Carnegie Institution, Washington, 1917, Xo. 251, 1-20, 14 figs.). 

 Experiments on Cassiopea xcmiachana show that nerve-conduction is due 

 to a chemical reaction involving the cations of sodium, calcium, and 

 potassium. Magnesium is non-essential. " The probably high tem- 

 perature coefficient of ionization of this ion proteid may account in some 

 measure for the high temperature coefficient of the rate of nerve- 

 conduction, which I find is 2 • 5 times as great as that of the electrical 

 conductivity of the sea-water surrounding the nerve." " Contrary to 

 Lillie's hypothesis, we have direct evidence that the rate of nerve-con- 

 duction may be independent of the electrical conductivity of the electro- 

 lytic solution surrounding the nerves." J. A. T. 



Swarms of Fresh-water Medusoids. — Harrison Garman {Science, 

 1916, 858). Millions of fresh-water medusoids appeared suddenly in 

 a Kentucky creek, not far from Lexington. They appear to be refer- 

 able to Caraspedacusta sowerhyi, which was first reported from the 

 Botanic Giirdens in Regent's Park. The hydroid phase was not found 

 in the Kentucky creek. J. A. T. 



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