NOTICES AND KEVIEWS. 223 



to have a mental treat, food for reflection, something to learn and 

 unlearn, something to add and much to subtract from their previous 

 tenets. Commencing with a statement of Nageli's conception that 

 the evolution of the organic world originated in virtue of inherent 

 internal forces, he states that there are probably few naturalists who 

 now adhere to it, and then plunges at once into the potency of external 

 influences, which one sees invariably to bring about ultimately all the 

 vital manifestations of animals and plants as reactions to such influences 

 and at the same time owns that we are " not yet quite clear " as to the 

 way in whicli external influences have formed and transformed 

 organisms. The remarks on hibernation (p. 9) will be of particular 

 interest to our readers, and after discussing the phenomenon of adapta- 

 tion by applying the principle of selection not only to the organism as a 

 whole, but also to its constituent parts (intra-selection), he illustrates 

 his farther arguments largely from the insect- world. The change in 

 coloration of the imagines of Polyommains jyJiloeas under varying tem- 

 peratures, and the dimorphism of Vanessa levana-prorsa are discussed as 

 also the protective resemblance of the larvae of the two broods of Lyccena 

 psendargiohs which vary in colour, the caterjiillars of the summer brood 

 being well protected on the white flower buds of Citnicifuga racernosa, 

 whilst those of the later brood are yellow or olive-green in colour, and live 

 on the flower buds of Acfiiiomeris squamosa, which, bears yellow flowers. 

 Reference is made to the variation of larva? under differing colour sur- 

 roundings, and the conclusion is arrived at that " in these and similar in- 

 stances, tlie dimorphism is not consequent on double sets of primary 

 constituents of which only one or the otlier can attain to development," but 

 that it " depends on tbe different susceptibilities of the histological elements 

 which in exquisite combination make up the skin." The " differentiation 

 of sex " next occupies attention, and the remarks on the neuters or workers 

 of state-forming insects — bees, ants and termites — must be read to be ap- 

 preciated. The conclusion, that poor feeding is not " the causa efficiens of 

 sterility, but merely the stimulus which not only results in the formation 

 of rudimentai-y ovaries, but at the same time calls forth all the other 

 distinctive characters of the workers," appears to be based on ju-etty safe 

 ground. The experiment detailed, too (p. 31), on Mnsca vomitoria, 

 could be supplemented by every British lepidoi^terist who pays attention 

 to the rearing of his specimens. The bearing of a starvation diet on 

 larvae and the resultant imagines is discussed, and the author states 

 that " the disappearance of a typical organ is not an ontogenetic but 

 phylogenetic i)rocess ; it never in any case depends on mere influences of 

 nutrition such as affect the development of each individual, but is always 

 due to the variations of the primary constituents of the germ, which to 

 all appearance can only come about in the course of numerous o-enera- 

 tions." Having given a definition of " ids " the secondary units, each 

 of which contains within itself all the primary constituents that are 

 necessary for the develoj^ment of an individual, contained in the o-erm- 

 plasm, the author discusses the production and development of workers 

 males and queens among the state-forming insects, and concludes that 

 " selection is the all-sufficient principle on which the development of 

 the organic world has been guided on its course." A brochure for every 

 scientific man to read, mark, learn and inwardly digest, it appeals with 

 especial force to those naturalists who are first and foremost entomologists. 

 — Ed. 



