upon lepidopterous larrte, dc. 299 



and beneath this again is a space filled with blood in 

 the everted organ, while in the centre is the retractor 

 muscle, made up of several bundles arranged round an 

 axial space, which contains a large ganglion. There is 

 little doubt that the blood penetrates the axial space 

 and between the bundles of the muscle. The muscular 

 tissue consists of striated fibres, and the bundles are 

 surrounded by a sheath which must be highly elastic. 

 The ganglion cells are very large, and their processes 

 are often seen to be continuous with nerve-fibres. The 

 proportion of nervous to muscular tissue is very large, 

 a fact which is doubtless correlated with the extra- 

 ordinary rapidity and extent of the muscular contraction 

 and relaxation during intro- and eversion respectively. 

 The extent of contraction is so great that the length of 

 the relaxed muscle must be some considerable multiple 

 of its length when completely shortened. All the 

 structural details above described are plainly indicated 

 in fig. 9. 



5. Additional eversible glands in larv^;. — I feel 

 sure that these defensive structures are of constant 

 occurrence in lepidopterous larvae. 



a. The larva of Liparis auriflua. — This larva, although 

 well protected by its irritating hairs, also possesses two 

 median dorsal eversible glands of an orange colour. 

 In the commonest variety of this larva there is a red 

 dorsal band traversed b}' a median black line, situated 

 over the dorsal vessel. The black line everywhere 

 divides the red band, except towards the anterior 

 margins of the 6th and 7th abdominal segments, where, 

 exactly between the two tubercles which bear the long 

 black hairs on each segment, a bridge of the red colour 

 unites the opposite halves into which the band is 

 divided, and the glands are present upon these bridges, 

 their orange colour being distinct against the surrounding 

 red. Another variety of the larva only possesses the 

 merest trace of the red band, and the orange glands 

 are therefore peculiarly conspicuous against a black 

 background. The glands are not often completely 

 everted, but they are very sensitive to tactile impressions, 

 and on stimulation a clear transparent secretion appears 

 in the lumen, being probably raised by partial eversion. 

 The secretion is not acid to litmus paper, but it 



