ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 807 



The embryology of Lhnulus is a very primitive type standing 

 nearer the branchiate arthropods than the tracheate, and on the whole 

 should be regarded as a generalized or a composite form, which with 

 its fossil allies, the Euripterida and Trilobita, form a class by them- 

 selves with a superficial resemblance to the Arachnida. The ultimate 

 origin of Limidus from the same stock as that which gave rise to the 

 modern annelids seems not improbable. 



Crustacea of Lake Baikal.* — Dr. B. Dybowski reports on the 

 large number of Crustacea which, as compared with members of other 

 groups, are to be found in Lake Baikal ; there were found 200 species 

 of Crustacea, 40 of molluscs, 20 of worms, 4 of sponges, 22 of 

 fishes, and 1 mammal. Of the Crustacea the Amphipoda are much 

 the most abundant. 



The author here limits himself to an account of the Isopodous 

 genus Asellus, of the four species of which two are new — 

 A. angarensis and A. baicalensis ; the two new species are described in 

 great detail. 



New Crustacean.f — Mr. Sidney I. Smith describes a new genus 

 of Crustacea from a single female specimen taken in the Caribbean 

 sea. 



Eunephrops n. gen. agrees with Homarus and differs from 

 Nephrops and Nephropsis in the number and arrangement of the 

 branchiae, and in the evenly swollen branchial regions ; it agrees with 

 Nephros and Homarus and differs from Nephrosis in possessing an- 

 tennal scales and well-developed eyes ; it agrees with Nephrosis and 

 differs from Homarus and Nephros in having very large antennal 

 spines, and in being without any spine on the second segment of the 

 peduncle of the antenna ; and it agrees with Nephros and differs from 

 Homarus and Nephrosis in having slender and carinated chelaj. The 

 species is named E. Bairdii. 



Vermes. 



Organization of the Hirudinea4— M. ^- Saint-Loup finds that 

 with regard to the nervous system of the Hirudinea, the nervous 

 system is always formed in the same way ; there is always a connective 

 cord surrounding the oesophagus, the two halves of which form on the 

 ventral surface of the body a double nerve-cord; the ganglia on 

 their course are formed by a fibrous band and six nerve-capsules 

 regularly disposed and containing unipolar nerve-cells. On each side 

 there are given off two lateral nerves which may be fused into a 

 common trunk and have on their course accessory nerve-cells. Closely 

 applied, and more or less fused ganglia form the chief part of the 

 subcofiophageal and of the posterior nerve-mass ; in the former there 

 are three or four, and in the latter a larger but variable number. 

 The nerves of the cephalic region must be regarded as taking their 



♦ Bull. Hoc. Nat. Moso., 1881 (188.5) pp. 17-57 (3 pis.). 



t Proc. U.H. Nat. MuKourn. viii. (IHK}) pp. KJT-TO. 



X Ann. Soi. Nat. Zool., xviii. (1K84) Art. 2, 127 pp. ^8 pl.M.). 



3 (i 2 



