CHIRONOMUS PRASINUS. G9 



body cavity ; and in certain situations, especially along the inter- 

 segmental folds of the thoracic segments, the substance of the 

 cells seems to be still more gathered up about the nucleus, so that 

 the cells project more strongly, and are drawn apart from each 

 other, thus breaking the continuity of the cellular layer. Where 

 this occurs, too, the cells lose their regularity of outline, and assume 

 a plastic, amoebiform appearance (see Fig. 2/!^b). 



These changes are not, I think, without their bearing on the 

 processes of growth of the larva. It need scarcely be pointed out 

 that we have not to do here with a cellular layer, whose elements 

 are in a formed, horny condition like those of the outer layer of 

 the epidermis in the human body. They more nearly resemble in 

 condition those ^of the inner layer or I'ete miicosiwi. If there is 

 a cell-wall at all, it must be of the thinnest and most delicate 

 description ; Lowne indeed describes the cellular layer beneath 

 the cuticle of the Blow-Fly as consisting of indurated pigmented 

 cells : and probably this is the case in the perfect insect, where the 

 processes of growth are completed, and no further increase is 

 required or can take place until the assumption of the imago state; 

 we see here, at least, that the hypodermic cells are in a highly vital 

 and plastic condition. The basement membrane of which I have 

 spoken, is only visible in living larvae under very favourable con- 

 ditions, such as the newly forming integument of the anterior feet. 



The organs of the mouth consist of a labrum, a labium, and a 

 pair of mandibles, the maxillae being only represented by a pair of 

 minute rudimentary palpi. These organs are represented in Figs. 

 13 and 14. The labrum is furnished with a number of minute 

 and variously formed hooklets, and with a row of very minute 

 chitinous teeth beneath (see Fig. 14). The mandibles are strongly 

 toothed, as is also the labium, on either side of which the integu" 

 ment presents a fan-like arrangement of radiating striae. The 

 mouth of this creature, both in its larval and perfect conditions, 

 presents great similarity to that of the Crane-fly, as described by 

 me some years ago in "Science Gossip."* 



The alimentary canal exhibits the following parts, viz. : the 

 oesophagus, proventriculus, ventriculus or chyle stomach, and the 



* (( 



Science Gossip," Vol. x., p. 155, and vol. xi., pp. 10, 171, and 201. 



