( 873 ) 

 SUMMAEY 



OF CUEEENT EESEARCHE3 EELATING TO 



ZOOLOOY AND BOTANY 



(jprincipally Invertehrata and Cryptogojmia), 



MICROSCOPY, &c., 



INCLUDING ORIGINAL COMMUNICATIONS FROM FELLOWS ANI) OTHERS/ 



ZOOLOGY. 



A. GENERAL, including Embryology and Histology 



of the Vertebrata. 



Mesoblast of the Vertebrata.f — Dr. 0. Hertwig here gives the 

 first part of bis full account of his studies on this subject, the pre- 

 liminary notice of which we have already noted.f He points out 

 that the object is to confirm the view enunciated by his brother and 

 himself in their tract on the coelom theory, in which they urged that 

 the middle layer of the Craniota arose, just as in the Chsetognatha, the 

 Brachiopoda, and in Amphioxus, from the epithelium of the archenteron. 

 The present part deals with holoblastic ova, the first example of which 

 is Triton toBniatus, a form admirably adapted for embryological inves- 

 tigation, especially when the ova are artificially fertilized ; as the 

 spermatozoa of this form live with difficulty in water, the author re- 

 commends their being transferred to 1 per cent, salt solution, to the 

 serum of the body-cavity, or to dilute aqueous humour. After a full 

 description of his method Dr. Hertwig proceeds to divide the history 

 of the development of the germinal layers into four periods. 



In the first of these we have the formation of the blastula and 

 gastrula ; in the latter there appear at some distance from the vege- 

 tative pole a small pit, which is the first sign of the commencing in- 

 vagination, and at the sides of the vegetative pole, and a little later, 

 a horseshoe-shaped groove — the mouth of the gastrula ; the gastrula 

 soon becomes bilaterally symmetrical, and the yolk takes up a ventral 

 position. During the whole of this period there is a continuous and 

 considerable superficial increase of the cell-membrane of the blastula ; 

 this is either effected by the growth and extension of the animal cells, 

 or by the increase and extension of the yolk-cells. 



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

 authors of the papers referred to, nor for the manner ia 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.") 



t Jen. Zeitschr. f. Naturwiss., xv. (1881) pp. 286-340 (4 pis.). 



X Ante, p. 575. 



