4 PRESIDENT'S ADDRESS. 



that formerly many forms of what has now been proved by 

 breeding to be one species, were described as distinct and 

 given separate specific names. Recent observations on the 

 Daphnids, a group of small Crustacea, shew great seasonal 

 variations in the same species, which will in like manner 

 tend to bring under one specific name various different forms. 

 It is clear that much remains to be discovered amongst the 

 smaller Crustaceans, as in an account of the Norwegian 

 species, out of 291 Copepoda enumerated, 40, many of which 

 were new to science, were added in 1910. To turn to insects, 

 those of the Seychelles Islands are peculiar in containing a 

 large proportion of species not found elsewhere. In the 

 Lepidoptera, this is the case to such an extent that more 

 than half of the total number are not known to occur in any 

 other part of the world. 



A very interesting discovery has been made with regard 

 to the light emitted by fireflies, which is found to have similar 

 qualities to those of the X-rays. The light passes through 

 wood, leather, flesh, &c., substances opaque to ordinary 

 light and affects photographic plates. It would be worth 

 while making experiments in this country with glow-worms, 

 to see whether their light has the same properties. Legis- 

 lation has been brought forward in the United States to 

 prevent as far as possible the introduction of insect pests. 

 Two of the worst, the gipsy and brown-tail moths, occur in 

 England, but are so rare that they do no damage. Very little 

 is known of the causes which determine the abundance or 

 scarcity of insects at any given time or place ; probably 

 climate and weather, the number of enemies that prey on 

 them, the abundance or scarcity of food, disease and other 

 circumstances are more or less responsible, and above all 

 their enormous fertility under favourable conditions enables 

 them to be abundant, even though they have been very scarce 

 in the previous year, This April, Caddis flies have swarmed in 

 my neighbourhood, in fact I have never seen so many about, 

 and one would hardly have thought that a hot dry summer 

 like the last would have encouraged their breeding. In a 



