OP THJE LARVA OF CORETHRA RLUMICORNIS. 71 



into tubes, wliich unite to form a common duct, opening on the 

 floor of the pharynx just inside the mouth, but not easily demon- 

 strated, owing to the superposition of various muscles and ganglia. 

 On the external surface of the Corethra some very delicate fan- 

 shaped tufts of hair may be seen, and from a careful examination of 

 them and their connection with the muscular and nervous systems 

 we may reasonably conclude that they serve as organs of touch. 

 They are situated in pairs, four on each segment of the body. Those 

 on the thorax are abundantly supplied with nerve-fibres of a larger 

 size than are given off to the other segments. The nerves pass off 

 from the large ganglia and enter ganglia at the bases of the hairs. 

 These ganglia are of a different character, being furnished with a 

 striated, cortex and a granular centre, and seem specialised organs, 

 of whose office I do not feel justified in speaking positively, but 

 they form most interesting objects of investigation when examined 

 in profile, for then we are enabled to make out the connection which 

 exists between the base of the hairs and the ganglion of the ventral 

 chain (fig. 2). Those situated on the other segments are more 

 simple in their character. They are attached to the integument by 

 their bases being inserted in a cup-like depression. On looking 

 through the transparent walls of the body, the root of each hair 

 will be seen in connection with a ganglionic body, from which we 

 can trace a nerve-fibre giving off branches to the muscles over which 

 it passes, and becoming merged in the central ganglion of that 

 segment (fig. 2). The office of these hairs seems to be that of 

 warning the larva of the proximity of danger, the contact against 

 these hairs conveying the irritation to the central ganglia, when a 

 reflex action is set up in the muscles, causing them to contract, and 

 producing those jerking movements by which Corethra manages to 

 evade any obstruction which may intrude in its path. Passing over 

 the intervening segments, which contain nothing specially to be 

 noticed, we come to the eighth, in which we observe two elongated 

 bodies filled with ovoid cells. In the earliest conditions of this 

 creature's existence these are clear spindle-shaped sacs filled with a 

 structureless protoplasm, but having a small collection of granules in 

 their central axis. After a time these granules become distinguish- 

 able as cells, filling the whole interior ; later still these spherical 

 cells become egg-shaped, while the fusiform sac becomes elongated 

 and tubular, and in them we recognise the characteristic ovisacs of 

 the Insecta. Now, having called your attention to the special 



