ON THE LAKVA OF ARCTTA CAIA. 265 



to en(|uire into final causes, but to investigate processes. His (question 

 is ever How, rather than Why." 



" May I ilhistrate this by a simple, perhaps too trivial, story, Avhich 

 derives its interest from its having been told of the childhood of one 

 of the greatest natural philosophers of the present century '? He was 

 even then possessed by that insatiable curiosity which is the first 

 <|uality of the investigator, and it is related of him that his habitual 

 question was, ' What is the go of it ? ' and if the answer was unsatis- 

 factory. ' What is the particular go of it ? ' That north-country boy 

 became Professor Clerk Maxwell. The questions he asked are those 

 which in our various ways we are all trying to answer." 



Whether the statement, or rather the summary of the learned 

 Doctor exactly states the case with regard to the vision of insects, it is 

 out of place to discuss here, but in the present condition of our know- 

 ledge, it is only in the most general way that we can speak of " pictures 

 being formed," or say " the field of vision is being mapped out a scon- 

 sistently as it is imaged on our own retina." So far as our present 

 information goes, vision in insects is of the most general character and 

 the whole area behind the hexagonal facets, including not only the retinal 

 cones at the back but also the semi-fluid material in front appears to be 

 capable of receiving impressions. A keen perception of light and shade, 

 and a distinct idea of masses of colour appear to be the main features 

 of insect vision. Discrimination of individual objects as we know them 

 appears to be impossible to insects by means of sight. 



My concluding remark must be one of regi'et, that among so many 

 entomologists who rear, catch and arrange the beautiful objects tliey 

 collect, there are still so many Avho amass collections, to show to their 

 friends, who spend infinite time and labour on breeding insects to 

 possess a series of a certain species in rather finer condition than those 

 of their entomological neighbours, and yet Avho never want to know 

 the " go " of it, and who could not answer a simple question relating 

 to the insects of which so many have passed through their hands. 



ojl I'fiE hEii:(i[ji OF ^ii^efi^ zmn, 



"With special reference to its correlated variations in Plumage, 

 Moulting and Hybernation. 



By T. A. CHAPMAN, M. D. 



A batch of eggs of A. caia came into my hands in the summer of 

 1890 almost accidentally. A bred $ was brought to me and I placed 

 her outside on a leaf ; looking next morning, she was still there and 

 had laid a batch of eggs. This led me to the experiments, some results 

 of which I here record, which I liad for a number of j'ears contemplated 

 making when opportunity offered. 



I may note that caia $ usually remains where she emerges till she 

 has paired, this takes jilace about midnight, the J leaves, and the ? 

 has usually laid a batch of eggs by morning. Being now less heavy 

 and bulky, she is able the next night to take wing, and afterwards lay 

 two or three more batches of eggs. The <? certainly pairs again, and 

 I think, from finding last batches of eggs less fertile, that the J does 

 so usiially also, after laying one or two batches of eggs. 



The oljservations I contemplated making on the larva of caia were 

 to be directed to the number of moults, which were said to vary much 



