Miscellaneous. 2o9 



From the ombryogenetic point of view the Gymnotoca are charac- 

 terized by the Trochosph.cera-\axv&, like the Arthropoda by the 

 Nauplius-embTyo. 



The phylogenetic table of the Gymnotoca given by M. Giard in 

 1876 may be compared with the genealogical tree of the Trochozoa 

 prepared by M. Iloule in 1889, and, according to the author, the 

 only essential alteration consists in the adoption by the latter of 

 Hatschek's term Trochozoa. 



In attempting to homologize the schizoccele of the higher Gymno- 

 toca with the eiiterocoele of the more archaic forms (Sagitta, Bra- 

 chiopoda), the fact that the original mesodermic cells in the schizo- 

 coelian types originate from the encloderm, at the margin of the 

 prostomium, in points perfectly homologous with those in which the 

 endodermic diverticula are formed in the enteroccelians, led the 

 author at first to regard the latter as representing the primitive 

 state, of which the derived (condensed) form is realized in the Mol- 

 lusca and Annelida. His later researches have enabled him to 

 generalize this interpretation and to formulate the following empi- 

 rical law : — • 



"When, in the development of allied animals, an organ originates 

 either by invagination or folding of a cellular lamella ( Wolffian 

 process), or bg the formation of a solid cellular mass which is after- 

 wards cleft or hollowed bg a cavity, the latter mode of formation must 

 be regarded as a condensation of the former." 



This formula may be applied to the Gymnotoca not only in the 

 question of the two forms of mesoderm, but also in the comparison 

 of the archigastrula (Sagitta, Erachiopoda) and of the derived modes 

 of gastrulation in the formation of the ventral nervous system by a 

 furrow (Salmacina, Protodrilus) and by thickening &c. With regard 

 to the nervous system and to the ectoderm generally the author states 

 that in no Annelid examined by him has he seen anything like the 

 syncytium described by M. lloule. The contours of the ectodermie 

 cells can always be shown by suitable reagents. — Comptes Roulus, 

 January 15, 1890, p. 90. 



On the Fauna of Mountain-lakes. By Dr. ¥. Zscuokke. 



The faunistic investigation of three neighbouring alpine lakes of 

 the Rluetic Alps, the dividing chain between Yorarlberg and Grau- 

 b iinden, gave the following results : — 



a. Lake of Partnun : elevation 1874 metres ; length 450, breadth 

 200, depth 35 metres ; temperature 9°-5-l0°-5 C. The basin is 

 enclosed by lofty rocky walls in the midst of the limestone moun- 

 tains ; its bottom consists partly of tine mud, partly of coarse gravel. 

 A green Algal vegetation is rather luxuriantly developed in the 

 lake, while the banks are scantily covered with plants. Almost 

 throughout the whole summer the basin receives a great influx of 



