158 Mr. Poalton's notes in 1885 upon 



surprise a complex form of "gland" was instantly 

 everted tbrongb the apertm-e, consisting of six diverging 

 processes of a light green colour, divided into two groups 

 of three each. It will be very interesting to investigate the 

 young stages of D. rinula in the light of this observation, 

 for it will then be possible to decide whether the ap- 

 paratus belonging to the latter is derived from an eversible 

 gland which has ceased to be eversible and has fallen 

 back into the condition with which all such structures 

 must have begun — a simple secretory involution dis- 

 charging its odoriferous or irritant contents ; or whether 

 the arrangement in D. vinula is truly ancestral, while 

 that of D.furcula represents a further advance. 



Since the above was written, I have been informed by 

 Lord Walsingham that a simple prothoracic gland is 

 present in the larva of Melitcea artemis, and that the 

 structure is everted, and hence becomes very prominent 

 in blown larvae. Lord Walsingham considered that the 

 secretion was of use to the larva in moistening its food. 

 On looking through the collection of preserved larva) we 

 also noticed other instances of the gland {e.g., in the 

 genus Catocala, &c.), so that it seems probable that the 

 structure will be found commonly in larvae. Hence it 

 appears that the defensive secretion and modified gland 

 of the genus Dicranura is a specialisation of an organ 

 which is probably used for a very different purpose by 

 many other larvai. Although the gland of D. rinula 

 seems to be intermediate between that of D.furcula and 

 of other larvae, I think it probable that the ontogeny of the 

 former larva will show that its gland at one time pos- 

 sessed all the complexity observed in that of D.furcula. 



8. The apparent failure of the extreme protection 

 OF MANY LARViE. — The larva of Dicranura vinula is 

 extremely well protected from insect-eating vertebrates, 

 and from hymenopterous and dipterous parasites. For 

 the former it has a terrifying attitude, and ejects a very 

 strongly smelling fluid ; for the latter it possesses the 

 flagella, and probably uses the fluid also. And yet the 

 larva is very subject to attacks of the latter kind, far 

 more so than many other larva; which are less protected, 

 and Weismann has shown that it is freely eaten by lizards. 

 It seems likely that the larva has been subject to attack 

 from a period anterior to the acquirement of the means 



