ZOOLOGY AND BOTA.NY, MICROSCOPY, ETC. 847 



Development of the Oram of PMlodina roseola.* — A. Billet has 

 taken advantage of the discovery of a number of these rotifers to 

 examine the early stages in the development of the ovum. He has, 

 it is especially interesting to note, been able to observe the formation 

 of polar globules, the existence of which in Eotifera has been denied, 

 while their apparent absence led the late Professor Balfour to his 

 well-known theory that polar globules are not found in partheno- 

 genetic forms ; the author believes, with Biitschli, that the polar 

 cells are the atavistic remnants of the globules excreted by Infusoria 

 during tbe process of conjugation, which are destined for the re- 

 generation of the nucleus. The phenomena of the appearance, dis- 

 appearance, and re-formation of the nucleus, and the formation of the 

 first segmentation-groove take place very rapidly — indeed, within the 

 space of one hour. 



The succeeding segmentation phenomena are also effected with 

 great rapidity, and the first organ to be differentiated is the mastax. 

 In common with preceding observers. Billet notes various points of 

 resemblance between developing rotifers and Bryozoa, and, in con- 

 clusion he promises to direct himself to the study of the winter and 

 summer ova, and the temporary appearance of male forms — questions 

 which must be studied before we can get to any complete account of 

 the embryology of the rotifera. 



New Swiss Rotatoria.f— Dr. 0. E. Imhoff records in a pre- 

 liminary communication the following species of Eotatoria from Swiss 

 Lakes. GonocMlus sp. differing from G. volvox in having black instead 

 of red pigment in the eye. Asplanchna helvetica, n. sp., most neaily 

 allied to A. priodonta Gosse ; resembles Leptodora hycdina in its 

 transparency and invisibility. He also describes and figures what he 

 calls Anurcea longispina n. sp., but which is A. cocUearis of Gosse 

 and described by him in Ann. and Mag. Nat. Hist., viii. (18-51) p. 202, 

 and A. spinosa n. sp. which is A. longispina of Kellicott, found by him 

 in Niagara water at Buffalo, U.S.A., in 1879, and described and figured 

 in Amer. Journ. Micr., iv. (1879) p. 20 and this Journal, ii. (1879) 

 p. 157. A species of Triarthra and one of Polyartlira are noticed 

 but not further described. 



Ecliinoderinata. 



Histology of Echinodermata.j: — So little is definitely known as 

 to the histological characters of the organs of the Echinodermata 

 that we may regard with satisfaction the fact that O. Hamann is 

 applying himself to the study. In his first communication he deals 

 particularly with the Holothurians, and has some notes on the nervous 

 system of star-fishes. 



With regard to the digestive tract he finds that the parts which 

 are macroscopically distinguishable diifer also in their structural 

 details ; thus, the oesophagus in its upper portion has only a circular 



* Bull. Sci. Dep. Nord, vi. (1883) pp. 1-10, 69-8i (2 pis. not published). 



t Zool. Anzeig., vi. (1883) pp. 466-71 (2 figs.). 



X Zeitschr. f. Wiss. Zool., xxxix. (1888) pp. 145-90 (3 pis.). 



