ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 653 



Rotatoria. 



Parasites of Rotatoria.* — O. Zacharias discusses the " sausage- 

 shaped parasites " of Rotifers. He gives a list of the forms in which 

 they occur (species of Brachionus, Asplanchna, Synchseta, Conochilw, 

 and Polyarthra). Various observers have noted and named them, but 

 their position remains uncertain. Zacharias thinks that the name lie 

 proposed in 1893 — Ascosporidium blochmanni — may be conveniently ad- 

 hered to. 



New Rotifers from Scotland.f — James Murray, in a short com- 

 munication, figures and describes the following seven new species of 

 Bdelloida, most of which he has obtained among Sphagnum from 

 Blantyre Moor in Scotland : Philodina brcvipes, acuticornis, decurvicornis, 

 and obesa ; Callidina ornala ; Rotifer quadrioculatus and spicatus. 



Key to the Rotifera for the Amateur. | — A friend, H. S. M., of 

 the late Thos. S. Stevens has published this revised and extended Key 

 to the Rotifera, which includes some of the new species described 

 since Hudson and Gosse's monograph appeared, but by no means all 

 of them. This Key is, no doubt, useful, but it will not be easy, and 

 hardly safe, to determine species by it alone. 



Echinodernia. 



Structure and Hermaphroditism of Cucumaria laevigata^ — A. 

 Ackermann gives a general description of this Holothurian, but the 

 chief interest of his investigation is in regard to the reproductive 

 system. The genital tubes arise as diverticula from a " budding zone," 

 which occupies the upper portion of the " genital-basis," and consists of 

 many canals abstricted off from the main canal. All these tubes are 

 hermaphroditic. Both in young and old animals a first portion forms 

 ova, a second portion is used up in follicle-formation, a third portion 

 becomes ultimately spermatogenetic. 



At the most posterior portion of the " genital-basis " only male 

 organs occur, which arise from the hermaphrodite tubes by a peculiar 

 process — the female elements being removed by the activity of phago- 

 cytes. Their place is taken by spermatogenetic cells, which arise from 

 an abundant multiplication of the indifferent sex-cells of the hermaphro- 

 dite tube. 



The animals function first as males, the male elements reaching 

 maturity first. Ripe eggs occur in the larger specimens, after a destruc- 

 tion of the previously developed male tubes. After the ova are removed 

 from the tubes and any remnants are destroyed by phagocytes, the tubes 

 become exclusively male gonads. From the first ovipositiou onwards 

 there is a continuous absorption of the oldest male tubes, and therewith 

 an absorption of the posterior " genital-basis." The absorption of ova 

 and of tubes is due to phagocytes — all of similar character — plasma- 

 cells with large nuclei. 



* Zool. Anzeig., xxv. (1902) pp. 647-9. 



t Ann. Scot. Nat. Hist., July 1902, pp. 1G2-7 (2 pis.). 



J Amer. Mod. Micr. Journ., May 1902, pp. 89-114. 



§ Zeitschr. wiss. Zool., lxxii. (1902) pp. 721-49 (1 pi. and 2 figs.). 



