AND DEVELOPMENT OF COMYS INFELIX. 239 



wliicli, one mass ])ecomcs predominant and forms the egg ; a portion of the isthmus 

 remains attached to the egg as its stalk oi' appendage. 



It is desirable to call attention to this, as I am not aware that any form of oogenesis 

 quite similar to this has been described. I may add that, when I had made only a few 

 observations, I thought it probable that the original mass of formative material divided 

 into two, and that we might find ourselves in the presence of a condition suggesting an 

 initial stage of dissociation of the embryo, but I was soon convinced that this was not 

 the case. The fact that chemical stains and reagents acted differently on the two masses 

 is of importance, indicating an essential dissimilarity in the nature of the two halves. 



(fi) Larva. 



In tracing the early life-history of the fly a serious practical difficulty is met with, 

 inasmuch as it is impossible to follow the same individual through the different stages, 

 for to be able to observe it in the scale it must be exposed, and thus killed. In this 

 way there is no certainty regarding the exact continuity of the observations ; I have 

 endeavoured to obviate this as much as possible by examining a great number of the 

 parasitized scales in all stages of growth and at all times of the year ; even so, I am 

 sorry to say that there are some links missing from the chain. 



General ])oints. — In preparing these larvae for the microscope, the best results were 

 obtained with those which had been removed from the Coccid, and then suspended on 

 a watch-glass in the vapour of osmic acid over the mouth of a bottle containing a 

 •5 per cent, solution. In a minute or two the larva3 look brown ; they are then washed 

 carefully in water and mounted in glycerine. Others were mounted in Canada balsam, 

 but in these preparations some shrinkage always occurred. Some I stained with borax- 

 or alum-carmine, but the osmic acid preparations possessed many advantages. This 

 applies also to the later stages in the metamorphosis before the pupal stage is reachel, 

 when the creatui-e becomes black and chitinous. 



i. First observed Stage. (Plate 11. figs. 10, 11, 12, 13.) 



External form. — I refer to this as the first " observed" stage, because it is probable 

 that the larva immediately on hatching may 1)C different from the youngest specimens 

 I have succeeded in finding ; the hypermetamorphosis may be greater even than that 

 which I shall describe. 



The larva of the fly is found in the younger Coccidai as a soft white tapering maggot 

 "75 mm. in length ; the head is not differentiated in any conspicuous way from the rest 

 of the body, the anterior end being merely bluntly rounded. Behind what may be called 

 the " oral segment " are thirteen segments, including the bifurcated tail-segment ; this 

 segment is a most unusual structure, for the body terminates in two long tapering tails, 

 each with a trach&al trunk continuing to its tip, suggesting that this is an adaptation 

 subserving respiration. These delicate pi'olongations are always embedded near the anus 

 of the host, and very frequently are capped with the old egg-case. The question of the 

 respiratory significance of this apparatus will be discussed later. 



SECOND SERIES.— ZOOLOGY, VOL. IX. 33 



