454 Proceedings of the Royal Physical Society. 



of Ustilaginese (99). The connection of periods of fasting 

 with the succeeding sexual climax has been repeatedly 

 noticed (82, 93). Barfurth has recently directed attention 

 to the importance of fasting in development (72, 73, 74, 

 75), and the title of one of his papers, " Der Hunger als 

 forderndes Princip in der ISTatur," is sufficiently suggestive. 

 Hoffman {S^, 89) notes some cases of the hereditary trans- 

 mission of characters acquired by certain plants as the result 

 of deficient nutrition. A starved Amphibian may be kept 

 for two years in larval form ; with insufficient food certain 

 insect larvae do not form the usual cocoon, and the pupae 

 are smaller ; starved caterpillars and tadpoles tend to become 

 males, and so on (83, 84, 87, lOlct, 108). Finally, there 

 are many changes, from the colour of feathers to the coating 

 of the stomach, which are well known to be associated with 

 changes of diet. 



In its influence, both on the vegetative and reproductive 

 systems, food is undoubtedly one of the most important en- 

 vironmental factors. To Claude Bernard, the whole problem 

 of evolution was very much a question of variations in 

 nutrition. " L'evolution, c'est I'ensemble constant de ces 

 alternatives de la nutrition ; c'est la nutrition consideree 

 dans sa realite, embrass^e d'un coup d'ceil a travers le 

 temps." 



III. Physical Envieonment. 



(Bibl. {a) 112-139 ; (6) 140-189 ; (c) 190-196.) 



(a) Heat (112-139). — It is well known that heat increases 

 ciliary motion, it also quickens the contractile vacuoles of 

 Infusorians, the rate of development and the advent of sexual 

 maturity (112, 113, 120, 127, 134, 135, etc.). In Artemia 

 Schmankewitsch (60) observed a direct relation between the 

 size of the gills and the rise of temperature; and the influence 

 of heat on the characters of Protozoa has been observed 

 (116), though Prommann's (118a) results on this subject 

 are mainly negative. Maupas (128) has recently made the 

 pretty experiment of increasing the rate of reproduction of 

 Stylonichia pustulata five times by an elevation of 17° C. in 

 the temperature of the surrounding water. In many cases. 



