ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 575 



INVERTEBRATA. 



Notes on the Fauna of the Caspian Sea. :!: — Dr. Einar Lonnberg 

 has had opportunity to collect and dredge in the northern part of the 

 Caspian Sea and at Baku. He gives some account of the temperatures 

 and bottom materials at various stations, and a list of the Invertebrates 

 collected, e. g. the light coloured Astacus leptodactylus, the abundant 

 Metamysis strauchi, Gmelina pusilla and Gammarus andrussovi (both 

 hitherto known from one specimen), Cardiophilus baeri, Micromelania 

 spica, Ampliicteis invalida, and the remarkable leech Archseobdella 

 esmonti. 



Of forms which are regarded as relicts from a former connection 

 with the Arctic Sea, he found only Cardium ednle. Although the water 

 had (in April and May) a relatively high temperature (13°-16° C), the 

 plankton was very sparse. Thus there were no fully developed plankton 

 Crustacea. One diatom and perhaps a dinoflagellate represented the 

 endemic plankton forms. 



Mollusca. 

 a. Cephalopoda. 



Development of Cephalopoda.f — Victor Faussek publishes a German 

 translation of his work on the development of Cephalopoda which appeared 

 in Russian in 1897, together with an additional article on the coeloin 

 question. The material for the research was chiefly furnished by species 

 of Loligo, notably L. vulgaris, and the aim was to complete the observa- 

 tions of Bobretzky by the use of modern technical methods. As to the 

 origin of the embryonic layers, the author finds that the endoderm is 

 represented by the " blastocones " which are the homologues of the 

 macromeres of other Molluscs, while the mesoderm arises from the ecto- 

 derm. The endoderm is entirely converted into the "envelope of the 

 yolk-organ " ( = perivitelline membrane of Vialleton) which is purely an 

 embryonic organ, so that no one of the permanent organs or tissues is of 

 endodermic origin. The mesenteron with all its derivatives arises from 

 the mesoderm, and generally the whole of the adult Loligo is formed 

 from mesoderm and ectoderm, the great development of yolk producing 

 total degeneration of the endoderm. The author quotes numerous obser- 

 vations of other authors in various groups of Invertebrates, to show that 

 this is not a phenomenon sui generis, but has its analogues elsewhere. 

 It can be brought into line with current embryological teaching by 

 regarding the mesodermic cells which produce the mid-gut as regenerated 

 endoderm, for the younger the embryo the greater the regenerative 

 capacity of its elements. 



In regard to the ccelorn, the author considers that the view of 

 Hatschek and Ed. Meyer, that it is to be regarded as having originated 

 from the cavity of the gonads in Turbellaria, finds no support in the 

 embryology of either Mollusca or Arthropoda. He believes that the 

 coelom of the higher Metazoa is, especially in embryonic life, of great 

 importance in excretion, and that it was primitively an excretory organ, 

 to be homologised with the excretory system of Platodes and Nemertines. 



* Ofversigt k. Vetensk. Akad. Forhandl., Ivii. (1900) pp. 13-29. 



1 MT. Zool. Stat. Neapel, xiv : (1900) pp. 83-237 (5 pis. and 11 figs.). 



