D. J. SCOURFIELD ON EPHIPPIA OF LYNCEID ENTOMOSTRACA. 223 



other we shall have to deal with. Like most other winter 

 eggs it is of a dirty greenish colour, for the most part quite 

 opaque, but with faintly translucent edges. 



Having now considered the detached ephippium, it will be 

 found very instructive to examine the shell of a living 

 ephippial female, especially with a view to discover if any 

 trace of the future ventral margin of the ephippium can be 

 seen. As a matter of fact, with critical illumination from 

 a substage condenser, and, say, a good ,y-in. objective, an 

 exceedingly delicate line, composed of what appear to be a 

 row of somewhat lozenge-shaped cells, can be made out 

 running across the ordinary shell markings in the exact 

 position where the ventral portions of the valves will eventually 

 break away from the rest to form the ephippium (Fig. 4). 

 The line cannot be traced all the way to the ventral margin 

 •of the shell, as it becomes very vague for some distance before 

 reaching i.hat point. Under a ^^-in oil-immersion this line 

 of weakness is seen to consist of a band of chitin free from 

 the ordinary " scratches " of the shell, but exhibiting numerous 

 minute " pits,'' and having along its centre a string of loosely 

 connected pieces of chitin. It is by the falling asunder of 

 these that the ventral portions of the valves become so easily 

 detached from the ephippium; and as they occupy only the 

 middle portion of the band above mentioned, there is a border 

 of pitted chitin left along the ventral margin of the ephippium, 

 as already noticed. One curious fact deserves mention in 

 this connection : namely, that where the line of weakness 

 crosses the ordinary shell markings, the latter, and also the 

 tiny intermediate scratches, turn aside from their ordinary 

 paths in such a way as to bring themselves more or less 

 parallel with the newly formed line. (See Fig. 5.) 



It should be mentioned that it is impossible to demonstiate 

 the line of weakness just described in preserved specimens of 

 ephippial females. It is necessary to have living animals for this 

 purpose ; and even then, rough and ready methods of examination 

 will not suffice to make out the structure satisfactorily. 



C amptocercus sirnilis Sars. 



Through the kindness of Professor Sars I have been enabled 

 to examine ephippial females of this South American species. 



