ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 57 



them investigated, but also on account of the fact that their investigation 

 will furnish many important details with regard to such problems as the 

 origin of lake-basins, the influence of environment and the laws of 

 variation. In addition they will furnish many interesting facts with 

 regard to the physical conditions of these faunal areas. It has already 

 been shown how important the presenci of the " Sprung schicht " is to the 



organisms in the lake. 



Tunicata. 



Development of Diplosomidse.* — A. Pizon has worked out the 

 development of Diplosomidae during the three weeks after hatching. 

 The facts described are remarkable. From the individual which is 

 hatched, there arises by budding a " bithoracic " individual which in 

 turn gives origin to an ascidiozooid " bithoracique et biventrique" which is 

 described as a " new physiological individual, much more complex than 

 the preceding, with two independent branchiae, two oesophagi super- 

 imposed, two stomachs communicating with the oesophagi, two hearts, 

 whose contractions are rarely synchronous, and two recti superimposed." 

 In the main, there are three remarkable phenomena : (1) the regular 

 regression of the old thorax in the bithoracic specimens ; (2) the persistence 

 of the abdomen from the one ascidiozooid to the other ; (3) the building up 

 of the "bithoracique et &wwtfr/^<e " ascidiozooids, and their final division 

 into two simple ascidiozooids with transformation of the visceral masses. 



Ova of Crustaceans and Gastropods.! — F. Henschen communicates 

 some notes on the structure of the immature eggs of Astacus fluviaiiUs, 

 Homarus vulgaris, Helix jJomatia, Linuuca stagnates, etc. In all these 

 forms he finds in some of the cells, chiefly those of medium size, 

 " pseudo-chromosomes " such as have already been described in various 

 ova by other observers. Their commonest position in Astacus is around 

 the nucleus forming part of a sphere, and enclosing a zone which is 

 sometimes distinguished by a greater granularity and sometimes by small 

 alveoli. With hajmatoxylin and eosin, they stain an intense blue. They 

 are straight or slightly bent and of a varying thickness ; the coarsest 

 consist of two threads lying closely together. He has no suggestion as 

 to their significance. 



Fauna of the Gulf of Trieste.}— Dr.Ed. Graeffe gives a list of the 

 Molluscoidea (Bryozoa and Brachiopoda) and Tunicata, with notes on 

 the time of appearance and spawning of certain species. No new forms 

 are enumerated. 



INVERTEBRATA. 



Mollusca. 

 y. Gastropoda. 



Olfactory Sen£e in Helix Pomatia.§ — Emile Yung states that there 

 are in the snail no groups of tactile, gustatory, or other differentiated 



* Comptcs Rendu?, cxxxvii. (1903) pp. 759-61. 



t Anat. Anzeig., xxiv. (1904) pp. 15-29. 



t Arbeit. Zool. Inst. Univ. Wien, xv. (1903) pp. 1-16. 



§ Comptcs Rendus, cxxxvii. (1903) pp. 720-1. 



