440 THE ZOOLOGIST. 



defence call forth yet more contrivances. Protective resem- 

 blance, concealment within burrows, by webs, by portable cases, 

 by fixed cases, by the transparency of the body, are a few of the 

 arts practised by aquatic insects, either in self-defence, or as a 

 means of pouncing unseen upon their prey. 



"The egg-laying of aquatic insects is attended with special difficulties, 

 some of which spring from the fact that the female fly is in general ill-fitted 

 to enter the element in which the earlier stages have to be passed. These 

 fresh difficulties are met by fresh contrivances. The egg-ropes of Chiro- 

 nomus, the egg-raft of the Gnat, the anchoring threads of the eggs of 

 Ephemera, the floating cocoon of Hydrophilus, are adaptations of peculiar 

 interest, Dytiscus, Notonecta, Ranatra, and certain Dragon-flies, lay their 

 eggs in incisions made in submerged plants. But even these carefully 

 hidden eggs are searched out by such egg-destroyers as Polynema, which 

 lay in them their own eggs, from which proceed the parasites which will, in 

 the end, devour their undeveloped host." 



One might go on to enumerate fresh contrivances under such 

 heads as the constructions of aquatic insects, the emergence of 

 the winged fly, the defences of resting pupse, and so on ; but 

 the subject is inexhaustible, and it must suffice to refer the 

 curious reader to the book itself from which we have culled these 

 few details. We must, however, make one more extract, and this 

 time from the Introduction. At page 24 Prof. Miall concisely 

 remarks : — 



" Aquatic insects make a capital study. While you are looking for one 

 kind, you will come across another. The same methods and the same tackle 

 will do for all. If a young student wants to observe the ways of living 

 creatures, we may recommend aquatic insects to him as an accessible and 

 very imperfectly explored field. He will find plenty of undescribed forms 

 and plenty of beautiful contrivances which no one has ever taken the trouble 

 to observe. But to make out the way in which the exquisite machinery of 

 nature is meant to work is no childish pursuit. The very attempt will 

 lead the naturalist to acquaint himself with scientific laws which seem 

 altogether foreign to Natural History ; it will exercise his industry and 

 sagacity; it will extend his knowledge of the possibilities of life." 



With these very pertinent remarks we cordially agree. 



