ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 651 



Palaeozoic Arachnida.* — Anton Fritsch describes and figures the 

 fossil Arachnida in the Museums of London, Paris, Dresden, Breslau, 

 and Vienna, along with those from the Coal-formation of Bohemia. 

 Thirty-nine genera aud sixty-seven species of Arachnida are recorded, 

 and more or less fully described in this important monograph. 



€. Crustacea. 



Entomostraca of Northern Swedish Mountains.t — Sven Ekman 

 has studied the Phyllopods, Cladocera, and free-living Copepods of the 

 various regions (birch-, grey willow-, and lichen-regions) of the Northern 

 Swedish mountains. The hydrographic conditions are on the whole arctic, 

 thus the ice-free period in the lakes of the birch region is from 8^-4 

 months, while higher up ice is never absent. Clear tabular summaries 

 show the composition and distribution of the Entomostracan fauna. On 

 the whole the forms are distinctively arctic, and there is close agreement 

 with those of the mid-European Alps. In the highest regions all the 

 forms are monocyclic, and in some cases the whole reproductive cycle is 

 condensed into lj-lf months, only the first generation consisting of 

 parthenogenetic females. There is more rapid growth than in the South, 

 and less temporal and local variation. The author discusses the in- 

 fluences of the Glacial period, the results of isolation, the present-day 

 splitting of a species like Bythotrephes longimanus into a northern and 

 a southern species, and much more that is both interesting and im- 

 portant. 



New Lerns8opod4 — Miroslav Miculicich found on the tunny {Thynnus 

 thynnus L.) an interesting new Lernasopod, which he names Thynnicola 

 eiegleri g. et sp. n. A brief description is given of both sexes. The new 

 form is nearest Tracheliastes, with which it is. compared in detail. 



Memoir on Gammarus.§ — M. Cussans gives a clear account of the 

 leading structural and developmental facts in regard to this w r ell-known 

 Amphipod. As a "Memoir' the work seems weak on the bionomic 

 side. 



The Origin of Mysis, Pallasiella, and Pontoporeia.||— M. Samter 

 and W. Weltner adduce a number of facts proving the origin of these 

 forms in an ice age. Mysis lives only in cold waters ; in summer in the 

 colder depths only, but in winter in all layers. Offspring are produced 

 only in water below 7° C, and twice in those lakes which are sufficiently 

 cold in autumn. Furthermore, it becomes larger and lives longer in 

 those waters which are specially cold in autumn. Pallasiella avoids the 

 higher summer temperature (contrast Gammarus). Reproduction reaches 

 its height in the cold time of the year, and more eggs per individual 

 are produced in spring than in summer. Pontoporeia, though living 

 in warm waters at all depths in winter, is absent in summer from all 



* Prag. (1904), 88 pp. 15 pis. and 99 figs. See also SB. Akad. Wien, cxiL 

 Keview in Geol. Mag, Decade V., i. (1904) pp. 471-5. 



t Zool. Jahrb. xx. (1904) pp. 1 -170 (2 pis. and 12 figs.). 



% Zool. Anzeig., xxviii. (1904) pp. 47-52 (3 figs.). 



§ Liverpool Marine Biol. Committee Memoirs, xii. (1904) pp. 1-47 (4 pis.). 



|| Zool. Anzeig., xxvii. (1904) pp. 676-94. 



