280 Scientific Proceedings, Royal Dublin Society. 



at 40° C, and found that they hatclied in four and a half daj's. Both Glaser 

 and we observed empty egg-shells on the cattle, so that it may be concluded 

 with some confidence that under normal conditions the egg is hatched in 

 about four days while still attached to the host animal's hair. 



Glaser has been fortunate in watching the actual operation of hatching, 

 and a summary of his aeeoimt of the process may well supplement our own 

 observations. The larva, as formed within the egg, was figured by Riley 

 ('92, p. 307), as possessing a spiny armature and strong mouth-hooks. We 

 describe below the newly hatched larva in some detail ; for the present it is 

 enough to call attention to the rows of backwardly directed spines on the 

 body-segments (Plate XXVI, figs. 31, 32), and the mouth armature with its 

 sharp median spine (fig. 3-3, M) and powerful paired hooks (fig. 33, H). Glaser 

 states that the larva, while still in the egg, moves freely, drawing both ends 

 away from the egg-shell, and bending the body. When ready to hatch, the 

 larva draws back its head from the end of the shell, and strikes strongly against 

 the free pole where it will emerge, the paired mouth-hooks then lying 

 parallel to the median spine. As soon as the shell has been pierced, the 

 maggot spreads its mouth-hooks widely apart, and tears loose little pieces of 

 the shell-wall. The larva begins to work at the middle of the egg-pole, and 

 extends its operation to the neighbouring region, till suddenly the envelope 

 gives way, and the maggot's head projects through the opening. It then works 

 its way out, segment by segment, the backwardly -directed spines preventing 

 it from slipping back. The whole operation of hatching takes, according to 

 Glaser, twenty- five minutes. 



The empty egg-shell (fig. 37) has a well-marked slit extending around 

 the lateral and front margin, where tliere is possibly a line of weakness, 

 despite the considerable thickness of the free pole of the egg. 



2. The Structure of the newi.y hatched Larva. 



As already mentioned, Curtice and Riley briefly described, and the latter 

 roughly figured, the unhatched larva of H. lineatum ('92, p. 307). Until the 

 observations made last year by Glaser in Germany, and by ourselves at Bally- 

 haise, the first-stage larva of Hypoderma had never been observed in the 

 free state. The " first-stage " larvse mentioned by various writers as found in 

 the gullets of cattle, are really maggots early in the second stage. For 

 example, the description and figures given by Jost ('07, pp. 672-7, pi. xxxii, 

 figs. 1-9) of the " first-stage " larva of H. bovis refer certainly to a small second- 

 stage larva, in which the minute spines and feeble mouth-hooks, recognizable 

 only with a moderate microscopic power, contrast most strongly with the 



