46 THE entomologist's record. 



substance the whole phenomena of heredity become inexplicable. The 

 simpler problems of entomology as presented in the larval, pupal, and 

 imaginal stages become impossible of clear explanation, while the more 

 complex ones become unthinkable, such as the varying number of 

 moults of certain larvae by the interpolation of an instar with a dis- 

 tinctive coat as Dr. Chapman found to be the case with Jocheaera aim, 

 or, the entire independence of the pupal stages of some species from 

 any influence of specialised larval characters, ejj., Staiirupua J'ayi, 

 and the marked reversal of this principle in others, for instance, 

 some Liparids and Pterophorids. Again how is it possible to 

 account for the problems of hybridisation, unless on the theory 

 of an elaborately organised germinal substance. In the hybrid 

 larva of SuicrhttltKsi ucdlatits S and papiili 5 , there is in the first 

 stadium, a balance of the characters of the male parent, later the 

 characters of the female parent become predominant, followed by an 

 oscillation back towards the characters of the male parent. The genital 

 organs of the male hybrids difler from those of both the parent species, 

 but shoAv no signs of inefficiency, those of a female specimen, however, 

 were gynandromorphic, yet the external sexual organs of the pupa of both 

 sexes show no tendency to any confusion of sex, nor dift'er in any respect 

 from those of the parent species in the pupal stage. With a theoretic 

 subdivision and organisation of the germ plasm, however, all these 

 problems are easily explained, Weismann's theory allowing of an 

 immense range of variability in its potentialities. His ultimate living 

 units or biophors are necessarily larger than molecules, being com- 

 posed of several at least of these inorganic bodies. Determinants or 

 iinits of control are composed of definitely arranged aggregations of 

 biophors, and are capable of setting up and controlling the growth aud 

 activities of parts of a cell or group of cells. The controlling principle 

 of the imaginal discs of a larva {tide, chapter on " Metamorphosis " in 

 Tutt's British Leindvptera, vol. ii), from which source the future legs, 

 wings, or other organs of the imago will be developed, would consist 

 of a group or sequence of determinants. Ids are units of the third 

 or highest grade, are made up of a series of determinants, and contain 

 all the potentialities for the development of the future organism. 

 Weismann remarks that theoretically a single " id " would be suffi- 

 cient for ontogeny. 



Even in his rejection of the transmission of acquired characters, one 

 would expect Weismann to meet with more support from entomologists 

 than from students of the vertebrata for example. It is comparatively 

 easy to understand how gemmules of increasing efficiency may bo 

 developed and given oft' from a developing muscle, nerve tissue or bone 

 of a vertebrate, but what chance have the nervures, scales, wing-mem- 

 brane, &c., of the wings of a butterfly of acquiring any characters 

 by use, save baldness and raggedness, or of developing and transmitting 

 improved gemmules once the wing has hardened sufficiently for flight ? 

 In this case, at any rate, progression must rely on the histonal selection 

 of William Roux, the intra-selection of George Romanes, the germinal 

 selection of Weismann, or panmixia, and not at all on use-inheritance, 

 the organs in question being incapable of acquiring any characters 

 during their period of active use. 



In concluding I would commend Weismann's works to all entomo- 

 logists who are not yet acquainted with them; they will at least enable 



