546 SUMIIARY OF CURRENT RESEARCHES RELATING TO 



SUMMARY 



OP CURRENT RESEARCHES RELATING TO 



ZOOLOOY AND BOTANY 



(principally Invertehrata and Cryptogamia), 



MICROSCOPY, &c., 



INCLUDING ORIGINAL COMMUNICATIONS FROM FELLOWS AND OTHERS.' 



ZOOLOGY. 



A. VERTEBRATA :— Embryology, Histology, and General. 



a. Embryologry.t 



Kinetic Phenomena of the Egg: during Maturation and Fecunda- 

 tion-l — Dr. C. 0. Whitman finds that the ookiuetic phenomena are 

 diversiform in the extreme, rarely present regular form-series, and so 

 stand in marked contrast with nuclear metamorphoses, which, every- 

 where, both in plant and animal cells, exhibit a most remarkable 

 uniformity. With regard to the movements of the germinal vesicle and 

 pronuclei, the author, fi'om the unique character of many of these 

 cytokinetic displays, refuses to consider them as the direct eflfect of 

 nuclear influence. Any hypothesis that refuses to admit that the cyto- 

 plasm is endowed with subtle powers of its own, is unable to account 

 for the characteristic difference between telolecithal and centrolecithal 

 eggs. The remarkable phenomena observed in developing eggs must 

 be due to the interaction of nuclear and cytoplasmic forces. There is 

 little evidence, in the explanation which is usually given, to support the 

 view that the pronuclear asters attract each other. When, however, a 

 careful analysis is made, we find three facts which can be said to furnish 

 indisputable evidence of attraction between tlie pronuclei. These are — 



(1) The curved path of the male pronucleus in tbe amphibian egg ; 



(2) The meeting of the pronuclei before reaching the centre of equili- 

 brium ; and (3) The centrifugal movement of the earlier pronucleus to 

 meet the more lately formed pronucleus. The author amplifies these 

 points. 



In discussing the receptivity of the ovum for spermatozoa, the dis- 

 tinction between receptivity and accessibility is very generally ignored. 

 Dr. Whitman believes that the period of receptivity may be said to date 

 from the moment the conditions of centripetal attraction are reversed in 

 the germinal vesicle. A period of non-saturation begins with the centri- 



* The Society are not intended to be denoted by the editorial " we," and they do 

 not hold themselves responsible for the views of the authors of the papers noted, 

 nor for any claim to novelty or otherwise made by them. The object of this part of 

 the Journal is to present a summary of the papers as actualbj published, and to 

 describe and illustrate Instruments, Apparatus, &c., which are either new or have 

 not been previously described in this country. 



t This section includes not only papers relating to Embryology properly so called, 

 but also those dealing with Evolution, Development, and Reproduction, and allied 

 subjects. X Journ. of Morphol., i. (1887) pp. 227-52. 



