ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 309 



a rod, the bifurcation of the extremities of this rod, and so on. In the 

 case of Ghiridota veuusta, however, Seuion has described the triradiate 

 origin of certain spicules. 



The quantity of lime respectively secreted by most Echinoderms 

 and by Holothurians differs greatly — in the former group the stroma is 

 packed with a calcareous stereom, whereas in most individuals of the 

 latter the skeleton is only represented by isolated spicules ; and 

 correlated with this difference is (a) the fact that in the former group 

 every scleroblast gives rise to a spicule, whereas in the latter at least 

 two scleroblasts have to co-operate for the same purpose ; and (b) the 

 equally cogent fact that in most Echinoderms the scleroblasts multiply 

 very rapidly (shown by the number of scleroblasts per spicule), whereas 

 in Holothurians they multiply very slowly. 



Meristic Variation in Common Sun-star.* — D. C. Mcintosh has 



examined 612 specimens of Solaster jmpposus. He gives the following 



variation table : — 



Total. 



612 



100 



It appears, therefore, that 12-, 13-, and 14-rayed forms account for 94 

 p.c. of the total. The curve of frequency is a simple uni-modal one 

 (Pearson's Type IV.). 



Hawaiian Echinoids.f — A. Agassiz and H. L. Clark make a pre- 

 liminary report on 2450 specimens of Echinoids collected by the 

 'Albatross' in 1902 among the Hawaiian islands. There are 49 genera 

 represented, 5 of which are new, and 67 species, of which 36 are new. 



Coelentera. 



Responses of Actinia. | — G. Bohn has investigated these with 

 particular reference to the effect of agitation of the water. In the 

 various species of Actinia this stimulus produces what he terms a kind 

 of " physiological misery," manifested by a marked tendency to retract 

 the tentacles which may disappear completely under an annular fold of 

 the body wall. Such a phenemenon is the most habitual response to the 

 different excitations which might harm the life of the individual. The 

 author, however, recognises differences in the character of the response 

 traceable to the time of the tides, hour of the day, purity of the water, 

 nature and solidity of the support, and so on. In short, when all the 

 factors are considered, the reactions of these and other shore animals 

 seem to be not vague but definite. 



Formation of the Skeleton in Hexacoralla. — Armand Krempf 

 discusses the cytological phenomena concerned in the skeleton-making 

 in Seriatopara. According to Heider (1881), the skeleton is due to the 

 juxtaposition of minute elements or calicoblasts, which are practically 



* Proc. Roy. Phys. Soc. Edinburgh, xvii. (1907) pp. 75-8 (1 curve), 

 t Bull. Mus. Comp. Zool. Harvard, 1. (1907) pp. 231-59. 

 X C.R Soc. Biol. Paris, Ixii. (1907) pp. 395-8. 

 § Comptes Rendus, cxliv. (1907) pp. 157-9. 



