ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1007 



being tlie most important, but placing several rotifers and Lepadellse 

 under the object-glass she waited until one of them would lay an egg ; 

 and the development taking about three days from the beginning of 

 the segmentation until the issue of the new animal from the egg, 

 she observed it continually throughout the first thirty to thirty-five 

 hours, with only short interruj^tions of two to three hours in the 

 observation of subsequent phases. This method has of course its 

 inconveniences by preventing sleep for two nights. It cannot be 

 applied also to those rotifers which live an errant life. These last 

 do not survive confinement, and must be kept in watch-glasses until 

 they lay their eggs, which last are then brought under microscopic 

 investigation. 



Ten different species were studied in this way, and proved to 

 undergo the same development, so that Botifer inflatus has been given 

 as a type of the development of the egg. The stages are all figured 

 in forty-eight drawings on the plate accompanying the memoir. 



New Rotifer.* — Mr. W. Milne describes a new rotifer, which he 

 places in the genus Pleurotrocha, though the jaws are each three- 

 toothed, and names P. mustela. It is exceedingly vigorous and active 

 in its movements, as well as most ferocious, striking out with trap- 

 like jaws at everything that comes in its way. When the jaws are 

 sbot out they open as they leave the oral opening and close with a 

 snap before the recoil ; but when irritated so swift is the stroke that 

 nothing of this can be seen. If the object struck is not too large or 

 hard the teeth fix and the head sucks into the victim " in the most 

 weasel-like way imaginable," holding on even when whirled round 

 and round. A case of lockjaio was observed by the author. In the 

 ovary may be seen only one perfect egg at a time, as large as one- 

 third of the body, and it is extruded before segmentation takes 

 place. 



The male is much smaller than the female, and has no mastax or 

 digestive apjiaratus. 



Echinodermata. 



Variation in Holothurians.f— Dr. K. Lamport in announcing 

 the preparation of a systematic monograph of Holothurians, discusses 

 the variability of some of their organs. He points out how the 

 arrangement of the ambulacral suckers varies with age ; he finds 

 that the calcareous deposits are much more constant, and mentions 

 only two cases of variation, to wliich Cucumaria frondosa at any rate 

 might have been added. He is dissatisfied witli the earlier classifica- 

 tions, but accepts completely Bell's proposed arrangement of tho 

 Dendrochirotae by the aid of their tentacles, and carries it further by 

 proposing to form two divisions to be called Monocyclia and Hetero- 

 cyclia, according as the tentacles arc in one or two circlets. He 

 takes tlie hint of Semper, to which Bell had directed attention, as to 

 the necessity of forming a fresh genus for some of tho Cucumariio, 



* Proc. Pl.il. Soc. Glasgow, xvi. (1885) pp. 188-93 (1 pi.), 

 t Diol. CciitralM,, v. (I8H.'-.) pp. 102-9. 



