( 7 ) 

 SUMMAEY 



OF CUERENT EESEAECHES RELATING TO 



ZOOL OGr Y AND BOTANY 



(principally Invertebrata and Cryptogamia), 



MICROSCOPY, &c., 



INCLUDDS'G OEIGINAl COMMUNICATIONS FROM FELLOWS AND OTHERS/ 



ZOOLOGY. 



A. GENERAL, including Embryology and Histology 

 of the Vertebrata. 



Rhythmical Chai'acter of Segmentation. f — Mr. W. K. Brooks 

 directs attention in a brief note to the fact that a nmnher of observers 

 have lately observed this phenomenon. Dr. Clarke has seen it in 

 the amphibian Amhlystoma, Mr. Brooks in the egg of an unknown fish, 

 and Wilson in Polych^ta and Oligochteta ; so too it has been seen in 

 the Arthropod Leucifer. The ova of these forms do not by any means 

 exhibit the same method of segmentation. Mr. Brooks is inclined to 

 find an explanation in the alternation of rest Tvith activity, and to 

 ascribe the change in shape dm-ing the resting periods to the physical 

 properties of the egg (its elasticity tending to render it spherical). 

 " In most eggs the yolk is not sufficiently elastic to allow any great 

 change of form, but careful time-records show that the process of 

 segmentation is rhythmical." It is to be hoped that the attention of 

 observers will be directed to this phenomenon. 



Secondary Yolk in the Germinal Vesicle of Mammalia 4 — 

 Prof. A. Eauber has a note on this subject. Induced by his discovery 

 in the yolk-sac of the embryos of young guinea-pigs, at the time of 

 the first circulation, of a number of formed elements. Inspection of 

 sections led to the view that they arose from the germinal vesicle. 

 The spheres of the yolk-sac agree in all essential points with the 

 elements of the yellow yolk (as e. g. of bii-ds). It seems, therefore, 

 to be certain that, like them, they are used for the nourishment of the 

 embryo. Some of this yolk, at any rate, owes its origin to the 

 epithelium of the yolk-sac. 



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

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

 may be expressed, the 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 irom 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.") 



t Amer. Journ. Sci., xx. (1880) p. 293. 



X Zool. Anzeig., iii. (1880) pp. 591-4. 



