( 929 ) 

 SUMMARY 



OF CURRENT RESEARCHES RELATING TO 



ZOOLOGY AND BOTANY 



(principally Invertebrata and Cryptogamia), 



MICROSCOPY, &c., 



INCLUDING ORIGINAL COMMUNICATIONS FROM FELLOWS AND OTHERS.' 



ZOOLOGY. 

 A. VERTEBR AT A :— Embryology, Histology, and General. 



a. Embryology.t 



Fertilization and Segmentation of the Animal Ovum.J— Drs. 0. and 

 E. Hertwig liave made a series of experiments on animal ova with the 

 object of affecting, by chemical, thermal, and mechanical agencies, (1) ferti- 

 lization, (2) the process of the internal phenomena of fertilization, and 

 (3) segmentation. 



In considering the mode of action of the reagents used, attention must 

 be given to the degree of concentration of the chemical reagents, and the 

 differences in the temperature applied; the time, also, during which the 

 modifying influence is allowed to exert itself is important. 



The movements of spermatozoa were found to be stopped by slight 

 doses of quinine or chloral, but as, on addition of fresh water, they recovered 

 themselves it is clear they were not killed, but only had their contractility 

 affected ; their reproductive power was not impaired. Morphia, moderately 

 strong solutions of strychnine, and nicotine seem to exert no influence on 

 spermatozoa ; a very strong solution of nicotine, acting for an hour, appears 

 to produce changes in the spermatozoa. 



The formation of the fertilization-sphere, or that elevation of the ovarian 

 protoplasm which marks the point of entrance of the spermatozoa, appears 

 to be affected by chloral or quinine; slight heating (up to 31° C.) produces 

 at first an increase in the size of the sphere; higher temperatures and 

 greater length of exposure have the same effect as quinine. Morphia, 

 strychnine, and nicotine have no effect. 



As to the effect of reagents on segmentation, it was found that • 6 per 

 cent, solution of morphia does not affect the ova, and that they will continue 

 to divide for a day in a 1 per cent, solution ; strychnine and nicotine have 

 no, but quinine, chloral, and heat have a distinctly weakening effect. Eggs 

 placed in water of 32° C. for ten minutes never completely regain their 

 power of segmentation. 



* 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 actually 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 Keproduction, and allied 

 subjects. 



t Jenaisch. Zeitschr. f. Naturwiss., xx. (1887) pp. 120-241, 477-510 (5 pis.). 



