76 THE ENTOMOLOGIST. 



germs of these forms are to be traced, ^^ chie%, to the evil influ- 

 ence on the sexual products exercised by the primary hybrid 

 parents ; and, secondly, in a lesser degree, to their own hybrid 

 origin. 



The appearance of a male-female form — that is, in outward 

 appearance — is, therefore, directly connected with this degenera- 

 tion and malformation of the egg-germs. It would be of great 

 interest to ascertain the condition of the genital products of 

 female hybrids capable of reproduction. The hybridization ex- 

 periments, recently tried with other Bombycid species, whose 

 female hybrids produce numerous and, to outward appearance, 

 normal eggs, can be used for such a study. 



It may here be observed, that the close correlation, which 

 undoubtedly exists between the structures situated in the centre 

 of an organism, the germ products, and the secondary sexual 

 characters situated on the outer periphery of the body — centri- 

 fugal relationships, as we may call them — make probable the 

 existence, on the other hand, of close correlation in a reversed or 

 centripetal direction ; that is to say, changes which a[)pear in 

 the periphery, also those which owe their appearance to factors 

 of the outer world, cause changes in the central organs, that is, 

 the egg-germs and their products. An influence in a centripetal 

 direction actually occurred in the frost experiments with regard 

 to the altered markings of Vanessa urticee, as the latter were 

 actually transmitted to the offspring. The warmth experiments 

 with the pupae of Rhodocera rhamni exhibit a singular example of 

 the resulting centrifugal influence. 



A number of females obtained by this experiment had almost 

 entirely taken over the male coloration. Those female individuals 

 which were experimented with, while throwing off the larval skin or 

 as fresh pupse, were especially influenced in the direction of male 

 coloration. But these latter also showed a distinct crippling of 

 the egg-germs, which could generally be observed from the out- 

 side, by a noticeable shrinkage of the whole abdomen of freshly- 

 emerged specimens. As a result of the latest experiments may 

 be mentioned, that the females of Saturnia ccecigena, Cup., 

 obtained feathered antennae, which otherwise are confined to 

 the male. 



These females were obtained from pupae, which were experi- 

 mentally compelled to hybernate, and these insects also showed 

 a decided and anatomically easily proved crippling of the egg- 

 masses. The experimental influence on the egg-germs is in 

 both cases bilaterally symmetrical, and following the correlative 

 alteration in the periphery of the body in an entirely systematic 

 manner, even when the change is only partial. These are, then, 



11 Compare 0. Hertwig (' Zeit und Streitfragen der Biologie.' Jena : 

 G. Fischer, 1894, pp. 120, Vll). 



