202 SUMMARY OF CURRENT RESEARCHES RELATING TO 



selection, and the necessity to admit a pliyletic or inborn power does 

 not exist. The possibility of the existence of such a power is rejected 

 by Weismann. 



The conclusions of Weismann are based upon a number of 

 EurojDean species. But it seems that the study of exotic species will 

 show that some of these conclusions cannot stand, or will lose at least 

 a large part of their value. The colourlessness of the newly-hatched 

 caterpillars is perhaps not without exception in some tropical species. 

 The succeeding green colour belongs to the hypodermal colours, but 

 all the longitudinal and oblique lines and the spots belong to the 

 dermal colours. The dorsal lines are the consequence of the situation 

 of the dorsal vessel ; probably the subdorsal line and the oblique 

 lines are muscular lines, and the stigma line a consequence of the 

 large longitudinal tracheae. The large eye-spots on the thoracic 

 segments indicate the place under which the wings are beginning to 

 be formed. Similar spots, but less strongly develoiied, are to be 

 found in a number of larvfe of Myrmelionida3. The formation of the 

 wings necessitates a largely accelerated circulation in those places, 

 and therefore an oxidation of the cuticula. These eye-spots belong to 

 the dermal colours. 



In some few instances the author has been able to observe how 

 the pattern is produced. In dragon-flies (Odonata) the thorax is 

 transparent and entirely colourless at the moment of transformation. 

 At this time the muscles are in process of formation. The thoracic 

 muscles of the Odonata are, as is well known, very powerful, and 

 rather exceptional in the shape of their tendons. Very strong 

 currents of the blood were observed just along the place where the 

 muscles were developing. The rush of the blood was very much 

 accelerated. Now just outside of these we find in Odonata dark 

 lines or bands, which appear to be the result of the formation of the 

 muscles. Uhi irritatio, ibi affluxiis ; therefore it is not imjDroper to 

 conclude that a powerful action in the development of the muscles is 

 here the cause of a stronger combustion and of an oxidation in the 

 adjacent parts of the external crust of insects. But not the pattern 

 of the thorax alone follows the lines of the muscles. On the head 

 we find a certain pattern corresponding to the muscles of the mandi- 

 bular apparatus ; another one on the segments of the abdomen corre- 

 sponding to the so-called respiratory or abdominal muscles, and 

 another one on the legs corresponding with their muscles. It is im- 

 portant to remember that those j)atterns are better and more definitely 

 developed in the most powerful flying Odonata, as in the ^schnina, 

 and especially in the Gomphina. The main colour of the Gomphina 

 is yellow of different shades, mostly greenish- yellow, and the stronger 

 the sj)ecies the larger is mostly the pattern of blackish bands. 



The same proceedings were observed in Cicada just emerging 

 from the nympha skin. On the head, thorax, abdomen, and legs 

 ajjpear similar patterns, corresponding to the muscles or to their 

 insertion places. In fact, where a stronger circulation exists in 

 insects, the part becomes more strongly chitinized and darker 

 coloured. 



Should this cxplauatiou of the facts be accepted we shall have 



