My dear M^r. Darwin

I find that I shall not be able to get a holiday till Saturday when I shall hope to see you unless I hear from you to the contrary.

As far as I know Kollikers paper on Chironomus¹ & Leuckart’s on Melophagus² are the only accounts we have of the embryology of the Diptera and in both these the embryo commences as an apod grub. The same is the case in Aphis and indeed it seems that while in the Crustacea the appendages appear rather before the segments, the reverse is the rule in Insects. Melophagus was supposed to be Pupiparous but Leuckart considers that the offspring is a larva. The case of Aphis is almost the same as that of the Orthoptera.³

My own feeling is that all Insects go through metamorphoses but that in some of them a part are passed before birth. Is not the so called larva of Orthoptera homologous (if I may use the expression) with the Pupa state of some other insects; and does not the grub of flies &c represent a stage which in many insects is passed in ovo. The metamorphoses of Meloe Sitaris &c shew I think that the changes of insects are not so uniform as they are generally considered to be. ⁴

Hoping you are pretty well I remain | Your affec^ate | J Lubbock

P.S. I am not quite sure if I have rightly understood the drift of your question, if not please write again | JL