34 SUMMARY OF CURRENT RESEARCHES RELATING TO 



entiated Gescldechtsniere in Holocephali. Furthermore, the caudal zone 

 is still very small relatively ; each segment has more or less dis- 

 tinctly its proper terminal canal ; and the caudal terminal canals have 

 not coalesced. 



In some Selachians, such as Acanthias, there is, as Aristotle noted, 

 only one ovary. This is well known ; but Redeke points out that in 

 some species of Batidae the same is true, and that in these the unilateral 

 development is expressed also in the whole genital tract. Thus in ten 

 specimens of Trygon pastinacea he found only a left ovary. Four 

 other cases of unequal development are noted, and it is always the right 

 side which tends to be rudimentary. The author seeks to correlate this 

 with the great development of the " spiral valve " of the intestine, which 

 may also affect the size of the kidney, as Howes has shown. There are 

 also in this paper some notes on the polyembryonic egg-capsule of 

 Trygon. 



Structure of Silurus.* — Dr. Maurice Jaquet gives an account of the 

 skeletal structure and musculature of this interesting fish. He entitles 

 his memoir, Researches on the Anatomy and Histology of Silurus giants 

 L., but there is as yet no histology. 



Sylvan Biology.f — Dr. 0. E. Imhof puts in a plea for a more syste- 

 matic study of " sylvestre Biologis"- — the bionomics of the woods, which , 

 as he rightly remarks, may have quite as much interest as is to be found 

 in the study of the fauna of lake and sea-shore and other habitats. He 

 gives an outline of the representative fauna from the Turbellarians and 

 Anguillulidae to the Limacidae and Helicidaa. He might have made his 

 " vorlaufige Notiz " stronger than he has done ; but many field-natural- 

 ists who are more at home in the woods than in or on the waters will 

 welcome his vindication of their possibilities of dealing, not merely on 

 terra firma, but in the shades of the woods, with the problems of biology, 

 as well as his suggestion of sylvan stations — in short of a scientific 

 " Walden" 



Fauna of Roumania.J — Progress is being made with the census of 

 Roumanian animals. Adrien Dollfus deals with a collection of Isopods, 

 of which Porcellio serialis is perhaps the most interesting ; E. Poncy 

 identifies a large number of Coleoptera ; and Carl Verhoeff names 11 Chi- 

 lopoda and 17 Diplopoda. The collections were all made by Jaquet. 

 A later instalment deals with Lepidoptera, &c. 



Plankton of Lake Leman.§ — Prof. E. Yung has followed Hensen's 

 method in studying the quantitative variations on the plankton of the 

 Lake of Geneva, but his results have led him to doubt the reliability of 

 the method. He finds that the plankton occurs at all depths ; that the 

 distribution is far from uniform, either horizontally or vertically ; that 

 during the day (especially in bright sunshine), the larger plankton 

 leaves the surface and descends to the depths ; and that there is a great 

 seasonal variation. 



* Bull. Soc. Sci. Bucarest, viii. (1899) pp. 129-78, 378-92 (21 pis.). 



t Biol. Centralbl., xix. (1899) p. 719. 



J Bull. Soc. Sci. Bucarest, viii. (1899) pp. 117-28, 365-77. 



§ Arch. Sci. Phye. et Nat., viii. (1899) pp. 344-64 (1 pi.). 



