1886.] On a Neiu Form of Direct Vision Spectroscope. 449 



that they are filled with processes from the follicular epithelium, and 

 that the egg is nourished in this manner. In the ova I examined I 

 could not see any processes, but they have been noticed by other 

 observers in larger eggs of fishes, as well as of reptiles and mammals. 



IY. The Follicular Layer. 



The follicular layer in the mature ovum consists usually of a layer 

 of closely-set cells, which, seen from above, have an hexagonal appear- 

 ance. A peculiar modification of the follicular cells is found in the 

 shanny's egg (Blennius pholis). On one-half of the egg's surface 

 the cells are elongated, their depth gradually increasing towards a 

 central point. In this way the depth of the cells varies from 

 0*007 mm. to 0*032 mm. I never noticed follicular cells passing 

 through the zona radiata, as has been described by many authors. 



Y. Development. 



No observation was made as to the origin of the egg, and it could 

 not be determined whether the ovum originated from a simple trans- 

 formation of an epithelial cell, or whether several unite, as in 

 " elasmobranchs." I am inclined to the belief, however, that Brock's 

 and Kolessnikow's views are correct, according to whom only one cell 

 is concerned in the formation of the primitive egg. In small ova the 

 follicular epithelium is composed of a few large cells. There are 

 several possible ways in which the follicular layer might have origi- 

 nated, either by an aggregation of epithelial cells round the ovum, 

 as in elasmobranchs, or by a collection of connective tissue cells at 

 the periphery of the ovum, or from the nucleus, as in many inverte- 

 brates. I have not been able to come to any definite conclusion on 

 this subject. 



The egg membranes appear after the follicle. The zona radiata is 

 formed first, and, as well as the zonoid layer, it takes its origin from 

 the yolk. 



Y. "Note on a New Form of Direct Yision Spectroscope." By 

 G. D. Liveing, M.A., F.R.S., Professor of Chemistry, and 

 J. Dewar, M.A., F.R.S., Jacksoman Professor of Natural 

 Philosophy, University of Cambridge. Received November 

 18, 1886. 



Direct vision spectroscopes are very useful in the observation of 

 shifting objects, such as auroras and other meteors. They are 

 generally in request for telescopic work, and also in all cases where 

 rapidity of observation is of consequence. Ordinary direct vision 



