ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



I'll 



veloping essentially as in the embryo throughout the life of the polyp. 

 Yet they arise from larger primordia involving larger numbers of cells. 

 This is true of the tentacles also. " It would appear that the phenomena 

 of regeneration are controlled primarily neither by considerations of 

 future significance nor geometrical relations, but by the differentiation 

 of the physiological mechanism in the region of development." 



Studies of Actinians.* — Ferdinand Pax gives an account of the 

 Actinian fauna of the "West indies, describing a large number of forms, 

 including the following new species: Gyrostomamncti-tliomse, Buhodosoma 

 kukenthali, Zoanthus poriticola, Palythoa hartmey&ri, Aiptasia lerodactyla, 

 Cystiactis koellikeri. 



He discusses the geographical distribution and the question of bi- 

 polarity. It has not been proved for littoral forms, it may hold for a 

 small minority of deep-sea forms, but on the whole it is very improbable. 

 The facts as regards Actinians do not support the Pendulation theory. 



The author's views as to the phylogeny of Actinians may be summed 

 up in a schema. 



Cerianthacea Actiniinse Zoanthacea 



Antipatharia 



Stichodacty 



Cerinula 



Tetracoralla 



campula 



The fine memoir is illustrated by a series of exceedingly beautiful 

 photographs. 



Geotropism in Corymorpha.t — H. B. Torrey has made observations 

 on the development of frustules that show gravity to be a factor con- 

 trolling the direction of their locomotion. Glass plates carrying several 

 hundred freshly laid eggs were fixed at angles of about 85° to the 

 horizontal. Gravity appeared to play no definite part in determining 

 the emergence of the embryos above or below the horizontal. The 

 frustules arose on the embryo always opposite the point of emergence. 

 But with elongation the clavate end of each frustule showed a distinct 

 tendency to migrate downwards, a positive geotropism of definite 

 mechanical value in the establishment of a holdfast firmly anchored 

 over a considerable area. 



Senescence in Hydroids.J — H. B. Torrey and A. L. Martin call 

 attention to progressive serial differentiation or senescence in some 

 hydroid skeletons. Successive hydrothecaa differ gradually in shape, 

 size, and sculpturing ; or the pedicels, when present, differ in the 



* Zool. Jahrb., xi. (1910) pp. 157-330 (10 pis., 46 figs, and 1 map). 

 t Publications Univ. California, (Zoology) vi. (1910) pp. 223-1 (1 fig.). 

 X Advance print, Proc. 7th Internat. Zool. Congress, Boston 1907 (published 

 1910), 2 pp. 



