( 725 ) 

 SUMMAKY 



OF CURRENT RESEARCHES RELATING TO 



ZOOLOaY AND BOTANY 



(^principally Invertebrata and Cryptogamia), 



MICEOSCOPY, &c., 



INCLUDING ORIGINAL COMMUNICATIONS FFxCM FELLOWS AND OTHERS.' 



ZOOLOGY. 

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



o. Embryology.t 



Primitive Segmentation of Vertebrate Brain-I — Mr. C. F. W. 



M'Clure cousiclers tliat the primitive vertebrate brain consisted of a 

 series of segments, similar to those found in the embryonic spinal cord, 

 and that the encephalomeres probably held the same relation to the 

 mesoblastio head-segments as the myelonieres do to their respective 

 mesomeres, that is, they were intersomitic, the centre of each neuromere 

 being opposite the sj)ace between two somites, and giving off a mixed 

 nerve from the apex. 



The region known as the encephalon is the result of a great differen- 

 tiation and specialization of the anterior segments of this primitive 

 structure. That differentiation first began and has been greatest in the 

 most anterior segments, and this may account for the greater size of the 

 folds in this region than in the hind-brain, in which less differentiation 

 has taken place, and which, therefore, conforms more to the vertebrate 

 type. 



Origin of Blood of Vertebrates.§ — Dr. H. E, Ziegler considers that, 

 phylogenetically, the blood- and lymph-vascular-systems were derived 

 from the primary coelom ; in ontogeny it may be seen that some of the 

 first vessels to arise are jiarts of the j)rimary coelom, and are gradually 

 shut off from it. The red blood-corpuscles arise ontogenetically from 

 solid venous rudiments, and in histological regeneration they similarly 

 arise from venous capilhxries ; the red blood-corpuscles, the specifically 

 respiratory cells, belong both in origin and function to the blood- 

 vascular-system ; they do not arise from the white corpuscles in the 

 blood, but have a similar origin witli them, insomuch as they are derived 

 from the histogenetic foundation of all the mesenchymatous tissues. 



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

 Qot hold themselves responsible for the views of the authors of the papers noted, 

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

 the Journal is to present a summary of the papers as actualli/ 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 Zool. Anzeig., xii. (1889) pp. 435-8. 



§ Ber. Naturf. Gesell. Freiburg, iv. (1889) pp. 171-82. 



