Natural Science 



A Monthly Review of Scientific Progress 



May 1899 



NOTES AND COMMENTS. 



Moulting as a Means of Defence. 



It was Romanes who said, " Wherever we tap organic nature it seems 

 to flow with purpose," and post-Darwinian naturalists have far excelled 

 the authors of the Bridgewater Treatises in the ingenuity of their 

 search for the utilitarian justification of occurrences. It must be 

 admitted, however, that there are some vital processes where the seamy 

 side is conspicuous, and one of these is ecdysis or moulting. The 

 expensiveness, the fatigue, the riskfulness of the process cannot be 

 ignored, even if the progress of research should make its physiological 

 inevitableness much more intelligible than it is at present. It is with 

 interest, therefore, that we note a communication by Ktinckel d'Herculais 

 (Comptes Rendus Acad. Sci., Paris, cxxviii. 1899, pp. 620-622) in 

 which it is pointed out that the moulting of insects is a means of defence 

 against animal and plant parasites. In seeking to infect young locusts 

 (Schistocerca peregrina Olivier) with the spores of the fungus (Lach- 

 nidium acridiorum Giard) which he discovered on the adults, 

 Ktinckel d'Herculais was struck by the fact that the repeated 

 moultings — every eight days — made the fixation of the spores on the 

 integument exceedingly difficult. Even if entrance be found through 

 the stigmata, the casting of the internal lining of the tracheae is 

 effectively antagonistic to infection. In the same way, the casting of 

 the intestinal lining was shown to free another species of locust 

 (Bchistocerea paranensis Burmeister) from a burden of Gregarine 

 parasites. Thus there is advantage as well as disadvantage attendant 

 on the physiologically inevitable process of moulting, and there is 

 some practical interest also in what the author has observed, since the 

 moulting will evidently tend to hinder the elimination of the locusts 

 by inoculation, — a method which has been of late regarded with some 

 hopefulness in various locust-infested countries. 



Nitragin and Nodules. 



One of the last communications on the much-discussed problem of 

 the nodules of leguminous plants is a paper by Miss Maria Dawson 



24 NAT. SC. VOL. XIV. NO. 87. 34I 



