204 SUMMARY OF CURRENT RESEARCHES RELATING TO 



excepted, are hypodermal colours. The dermal colours are formed 

 during the transformation before the integument becomes rigid. The 

 hypodermal colours are formed either after this period or as a main 

 colour in previous stages, just after hatching, before any pattern exists. 



After a discussion of mimicry in colours, the nature of colour and 

 its formation is dealt with, the author's view being that it is probable 

 that the colours of insects are chemically produced by a combination 

 of fats or fat acids with other acids or alkalies by the influence of air, 

 light, and heat. 



The author's " final conclusions " are as follows. 



" 1. That some colours of insects can be changed or obliterated by 

 acids. 2. That two natural colours, madder-lake and indigo, can be 

 produced artificially by the influence of acid on fat bodies. 3. As 

 protein bodies in insects are changed into fat bodies, and may be 

 changed by acids contained in insects into fat acids, the formation of 

 colours in the same manner seems probable. 4. That colours can be 

 changed by different temperature. 5. That the pattern is originated 

 probably by a combination of oxygen with the integuments. 6. The 

 mimicry of the hypodermal colours may be effected by a kind of 

 photographic process. 



In comparing these still insufficient data with the statement — 

 that colour and pattern are produced in a purely mechanical manner, 

 and are the consequences of natural selection, of adaptation, and of 

 inheritance — we must, if we want to go beyond belief, directly 

 exclude inheritance, as after the statement of Prof. Weismann him- 

 self, it is entirely unknown how inheritance works ; even the question 

 itself is still entirely untouched. We must further exclude natural 

 selection and adaptation, as both are (according to Prof. C. Semper) 

 only able to begin to work after pigment is produced and after a 

 change of the pattern has begun. 



What is then left to justify our accepting a purely mechanical 

 manner but the simple belief that it is so ? 



I am convinced that colour and pattern are produced by physio- 

 logical processes in the interior of the bodies of insects." 



Development of the Excretory Generative Ducts in Insects.* — 

 The types examined by J. Nusbaum in his study of this subject are the 

 Pediculina, Lipeurus bacillus and Goniocotes hologaster, and the Cock- 

 roach, Blatta orientalis. His conclusions are stated as follows : — 1. 

 The assiunption is incorrect that the posterior cords of the rudiments 

 of the sexual glands unite with each other and form the origin of the 

 whole excretory channel ; these cords only form the vasa deferentia 

 or oviducts. 2. All the other parts of the excretory apparatus, viz. 

 uterus, vagina, receptaculum seminis, ductus ejaculatorius, penis and 

 accessory glands, arise from the dermal epithelium. 3. The outer 

 connective-tissue sheaths and the musculature of the excretory ai^para- 

 tus originate from the mesodermal cells of the body-cavity. 4. The 

 excretory passages commence as paired germs. All unpaired parts 

 (uterus, penis, receptaculum seminis, azygos glands, &c.) arise from 

 paired rudiments. The unpaired excretory apparatus of Insects must 



* Zool. Aijzcig., V. (1882) pp. G37-13. 



