ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 161 



off by peritoneal walls from the coelom. Lang's trophocosl theory is 

 confirmed. 



Stolon-formation in Trypanosyllis.* — F. A. Potts describes in four 

 species of TrypanosyJUs the formation of stolons from a cushion of 

 proliferating tissue at the posterior end of the stock. They are formed 

 in successive transverse rows of seven or eight, the number produced by 

 a single individual being between 100 and 200. New rows are estab- 

 lished at the anterior end pushing those already formed backwards so 

 that the oldest stolons are most posterior. Ectoderm and mesoderm 

 alone take part in the formation of the stolons, so that they are without 

 a,n alimentary canal. 



The following stages were distinguishable : 1. The aggregation of 

 leucocytes in the posterior segments, which invade the mesoblast of the 

 proliferating cushion. 2. The appearance of centres of proliferation in 

 the epiblast, which cause the formation of stolons. The mesoblast 

 advances and fills up the hollow processes formed by the ectoderm. It 

 lies at first in close association with the ventral surface of the stolon. 



3. The mesoderm proliferates and segments. Septa are formed. 



4. The stolon is invaded by two bundles of muscle-fibres from the 

 stock, and by a single ventral nerve-cord. 5. The ectoderm is seg- 

 mented and various structures appear. The gonads arise as lateral 

 outgrowths from the central mesodermic mass. With the growth of 

 the stolons the proliferating cushion is gradually absorbed. 



Neniatoh.elniinth.es."' 



Experiments with Eg^s of Ascaris megalocephala.t — E. Faure- 

 Fremiet immersed a number of fertilized eggs in oil of vaseline, and 

 exposed them to air after three months and a half. They showed four 

 degrees of cytolysis. In the first two degrees there was a considerable 

 augmentation of chromatin ; the chromosomes were of the normal size, 

 but four times as numerous. The number was perhaps variable. The 

 increase of chromatin does not occur during the time when the ^gg is 

 bereft of oxygen in the oil. The eggs which do not develop at all 

 because of more advanced cytolysis only showed four chromosomes. 

 The increase must take place after the exposure to air. In some cases 

 the ovum divided into a nucleated and a non-nucleated blastomere ; the 

 former followed the normal plan of development, or formed a he mi- 

 embryo. Other peculiarities in the postponed development are recorded. 



Chromatin Diminution in Ascaris Blastomeres.f — 0. Zacharias 

 finds that in the nuclei of the blastomeres of Ascaris megalocephala 

 bivahfis, the chromatin material of the old " theloid " nucleus goes 

 entirely into a state of solution, and that a replacement nucleus (or 

 epikaryon) appears in its place, being reconstructed afresh from the 

 cell-plasma of the blastomere. 



* Quart. Journ. Micr. Sci.. Iviii. (1913) pp. 411-46 (2 pis. and 8 ngs.). 

 t Bull. Soc. Zool. France, xxxvii. (1912) pp. 285-8 (4 figs.). 

 X Anat. Anzeig., xliii. (1913) pp. 33-53 (2 figs.). 



