C 41 ) 

 SUMMAEY 



OF OUEEENT RESEARCHES RELATING TO 



ZOOLOdY AND BOTANY 



(principally Invertehrata and Cryptogamia), 



MICROSCOPY, &c., 



INCLUDING ORIGINAL COMMUNICATIONS FEOM FELLOWS AND OTHERS.' 



ZOOLOGY. 



A. VERTEBR AT A :—Embryolo gy, Histology, and General. 



a. Embryology.t 



Embryonic Ganglion-cells.J — Prof. W. His states that in human em- 

 bryos, at the conclusion of the first and at the beginning of the second 

 month of development, the cells of the spinal ganglia are bipolar. Of 

 the two processes, that which is dorsally placed passes into the hinder 

 column of the cord, while the ventral makes its way to the motor root- 

 fibres to go still further in a peripheral direction in their company. The 

 processes commence with a conical piece of attachment, but narrow to 

 thin fibres with the character of cylinder-axes. They are not connected 

 with the middle, but with the sides of the cell-body. The nucleus is 

 generally excentric in position, and is succeeded by a more or less broad 

 zone of protoplasm, from the marginal portion of which the two processes 

 pass out in opposite directions. This stage may be regarded as preliminary 

 to the formation of T-shaped fibres. For satisfactory observations at this 

 stage, the ganglion must be free from connective-tissue elements, and have 

 no special investment. 



Development of the Mole.§ — Mr. W. Heape, in the course of this paper, 

 notes the early appearance of the optic grooves, the formation of the amnion 

 first at the hinder end of the embryo, and the folding off of the head end 

 of the embryo only. Though the optic vesicles begin to appear early, their 

 development is soon checked, doubtless in consequence of the habits of the 

 adult. A complete tube or ueurenteric canal becomes developed posteriorly ; 

 this is the homologue of the median dorsal diverticulum of the enteron of 

 AmpMoxus, and it is to be noted that while it there gives rise to the 

 notochord, it almost completely disappears in the mole before the notochord 

 begins to be formed. As, however, the notochord becomes isolated by the 

 ingrowth of the lateral hypoblast below the axial cells, and as it is formed 



* 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 Reproduction, and allied 

 subjects. 



t Ber. Verhandl. Gesell. Wiss. Leipzig, 1886, p. 290. 



§ Quart. Joum. Micr. Sci., xxvii. (1886) pp. 123-63 (3 pis.). 



