478 SUMMARY OP CURRENT RESEARCHES RELATING TO 



SUMMAEY 



OF CURRENT RESEARCHES RELATING TO 



ZOOLOGY AND BOTANY 



(principally Invertebrata and Cryptogamia), 



MICROSCOPY, &o., 



INCLUDING ORIGINAL COMMUNICATIONS FEOM FELLOWS AND OTHERS; 



ZOOLOGY. 



A. GENERAL, including Embryology and Histology 

 of the Vertebrata. 



Division of Embryonic Cells in the Vertebrata. f — L. F. Henne- 

 guy, in studying cell-division as exhibited in the ovum of osseous 

 fishes, finds that that of the trout, on the third or fourth day after 

 fecundation, if treated with a mixture of acetic and picric acids, is the 

 best adapted for this investigation; the cells are then seen to be 

 formed of a finely granular protoplasm, and contain a nucleus of some 

 size. 



The nucleus of a cell in a state of repose contains a plexus, formed 

 of small irregular granulations, which are especially well stained by 

 carmine. The nucleolus is only a little larger than the other granu- 

 lations. Soon there appears around a clear space, of which the centre 

 is occupied by the nucleus, very fine clear lines, which are set along 

 the rays of the cell, and which together form an aster ; this aster 

 elongates and becomes elliptical, as does also the nucleus ; the aster 

 then divides, and the two halves each form a fresh aster; at this 

 moment the membrane of the nucleus disappears, and the rays of the 

 aster penetrate into the interior. The plexus now breaks up into a 

 number of small rod-shaped bodies ; these become set at the extremities 

 of the rays, and form the so-called equatorial plate. Gradually the 

 rods diminish in size but increase in number, and fuse to form a 

 pectinate figure. The body of the cell then begins to be constricted 

 in its middle, the rays of the aster disappear, and the connective 

 filaments alone remain to unite the two nuclei, until at last the cells 

 become completely separate. The new nucleus, due to the fusion of 

 the rods, is highly refractive, and is intensely coloured by reagents ; 



* The Society are not to be considered responsible for the views of the 

 authors of the papers referred to, nor for the manner in which those views 

 may be expressed, the main object of this part of the Journal being to present a 

 summary of the papers as actually published, so as to provide the Fellows with 

 a guide to the additions made from time to time to the Library. Objections and 

 corrections should therefore, for the most part, be addressed to the authors. 

 (The Society are not intended to be denoted by the editorial " we.") 



f Rev. Internat. Sci. Biol., ix. (1882) pp. 363-5. 



