96 OBSERVATIONS ON PERIPATUS, 



In the favourable summer of 1894-5, the individual adult 

 Peripati ranged very much larger in size than was the case in 

 1895-6. The dry conditions of the latter period appeared to 

 have stunted the growth of the creature. In 1894-5 large 

 numbers of females were H inches in length when crawling, 

 not counting the antennae, and the males 1 inch; while in 1895-6 

 the longest female seldom exceeded 1 inch and males aljout | inch. 

 These are the dimensions when crawling naturally, and not when 

 stretched to the fullest extent. What became of the large 

 sized individuals of 1894-5, I cannot say. They may have 

 perished, or could they have shrunk in size as a result of the 

 unfavourable conditions 1 Whatever may be the cause, their 

 absence was very marked. 



In his account of the Mammalia of the Horn Exj^edition,* 

 Professor Spencer gives exceedingly interesting information on the 

 effect of the prolonged spells of arid conditions on the bodily 

 development of some of the mammals of that region; and of the 

 remarkable manner in which, on the other hand, they respond to 

 the more favourable state of matters when a wet period inter- 

 venes. 



A somewhat analogous series of observations is quoted in 

 Nature from The Entomologist,^ in which Standfuss, of Zurich, 

 has investigated the effect on the dimensions, and on the patterns 

 and colours of the wings of certain butterflies; of the sub- 

 jection of the eggs, larvae and pupse to various periods of exposure 

 to different conditions of heat, cold, and moisture. Amongst 

 other results arrived at was this, that the effect of abnormal heat 

 on the larva was to hasten the development, but to cause a notable 

 reduction in the size of the wings. 



A very noticeable peculiarity was the intensely local nature of 

 Peripatus. Considerable numbers would be met with in a very 

 restricted area, and without any apparent cause none at all, or 

 very few, would be found on precisely similar ground adjoining. 



* Account of the Horn Expedition to Central Australia, Part 2, 1896. 

 t "Nature," Vol. liii., 540, April, 1896. 



