1887.] 173 



walls (I could not find it8 head-quarters) ; and one or two Hylastes ohscurus, by 

 casual sweeping. Acritus punctum continued to occur in fair abundance up to the 

 end of May, but only one more Pentarthrum Huttoni (p. 17) was obtained, in 

 exactly the same spot as the first two specimens, though I spent a good deal of time 

 in endeavouring to trace the insect to its head -quarters. 



H.M.S. " arappler," Gibraltar : 

 November 4th, 1886. 



FURTHER NOTES ON THE DEVELOPMENT* OF THE EMBRYO 

 IN EaaS OF BOTYS HYALINALIS. 



BY W. E. JEFFBET. 



On the 1st o£ August last, having secured a batch of nine o£ these 

 singularly flat and transparent eggs laid on a slip of glass, T kept them 

 under the microscope during the 12 days of incubation, watching 

 them as frequently as possible, and making notes of what I saw. 



As some extracts from these notes may interest your readers, I 

 make the following selection : — 



When first laid, the contents of the egg seem of a perfectly 

 homogeneous fluid nature. 



In 8 or 9 hours after, the contents show as fine granules of yolk 

 slightly denser in the middle of the egg — the blastoderm can be 

 already traced as an extremely fine marginal line, which, at some parts, 

 the granular contents did not quite reach, the margin of reticulated 

 chorion showing as a clear space all round. 



When about 12 hours old, the mass of yolk-granules were observed 

 to be closer to blastoderm all round, but the outline of the latter had 

 become irregular and depressed on one side. 



In 15 hours, this depression had increased to a sharp angle, but 

 in another hour, had returned to its original contour, only with a 

 slightly increased space of clear shell beyond. 



When 22 hours old, the margin was observed to be crenated with 

 protuberances — from the aggregation of granules having the appear- 

 ance of nucleolated cells — but general contour regular. 



These irregularities of the margin of the yolk-sac had increased 

 by next morning, with one large, almost triangular, hump at one place. 



Some 28 hours had now elapsed since the eggs were laid. 



When 30 hours old, the first faint signs of transverse septa noticed, 

 caused apparently by the folding in of the yolk sac to form the amnion. 

 It had the appearance of a melting away of the granules. 



* Dr. Osborne has an article on this subject in No. 242 of Science Gossip for Febraary, 1885, 

 where, at p. 33, a few figures are given. 



