ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 419 



difficulties found in investigating the depths at which it lives (20-25 

 metres), in spring and autumn — the only suitable seasons for these 

 ■crustaeea. The absence of Pallasiella from the Vilm-See is explained 

 by the fact that it is too shallow to allow of a summer migration to 

 •colder water, which always takes place in the other lakes. 



Annul at a. 



Histology of Oligochaetes.* — Dr. M. de Bock finds that the "muscu- 

 lar columns " which constitute the musculature of the body- wall in 

 Oligochretes are bundles of fibres enveloped in a fine membrane. The 

 •fibres are made up of muscular elements, not further divisible, and 

 formed of contractile substance. These elements originate from myo- 

 genic cells, each of which produces several elements. In the Lumbri- 

 cidre, the muscular columns tend, especially in the longitudinal layer, to 

 arrange themselves in compartments, bounded by a distinct membrane 

 originating from the connective-tissue. This connective-tissue contains 

 nuclei, but the cell-boundaries have disappeared. The lateral line of 

 the Limicoline forms is due to the fact that the muscle cells tend to 

 have their nuclei aggregated in special regions, where they are raised 

 on peduncles. The lateral line has no nerve, but contains a vessel, 

 Apparently of lymphatic nature. 



Malayan Oligochaetes."]" — Prof. D. Rosa describes a small collec-' 

 tion from Sumatra and Amboina, including one species of Pontoscolex 

 and six of Plieretima, one of the species of the latter genus being new. 

 The new species, P. picteti, though well defined, is nearly related to P. 

 Jwulleti and P. tobaensis. 



Hypodermic Impregnation of Hsementeria costata. f — Prof. H. 

 Bolsius figures some sections of this leech which throw light upon the 

 manner in which the spermatozoa, set free from the hypodermic sperma- 

 tophore, penetrate the uterus. One of the sections shows the free 

 spermatozoa aggregated in masses about the nerve-end and the uterus, 

 and another shows that the periphery of the uterus is traversed by nu- 

 merous canaliculi with funnel-shaped openings, into which the sperms 

 pass. The section does not show canaliculi throughout the thickness of 

 the uterine wall, nor openings into its central lumen, but the author 

 believes that this can be explained as due to the sinuous course of the 

 canaliculi. His general conclusion is that the spermatozoa reach the 

 uterine lumen by predetermined paths, and not by perforating the wall, 

 as Kowalevsky supposed. 



Leeches of Illinois. § — J. Percy Moore gives a descriptive catalogue 

 of the Hirudinea of this State, with notes on the habits, the food of the 

 different forms being treated in especial detail. 



Nematoh.eliirinth.es. 



Segmentation in Nematode Embryos. || — Prof. Ludwig Ehumbler 

 has studied living young of Rhabdonema nigrovenosum removed from the 



* Rev. Suisse Zool., ix. (1901) pp. 1-41 (2 pis.). t Tom. cit., pp. 131-6. 

 I Zool. Anzeig.. xxiv. (1901) pp. 195-8 (2 figs.). 

 § Bull. Illinois State Lab. Nat. Hist., v. (1901) pp. 479-547 (6 pis.). 

 || Anat. Anzeig., xix. (1901) pp. G0-8S (21 figs.). 



2 F 2 



