HOMOLOGY AND ITS INTERPRETATION 49 



the termites are very fond, and thereby render their possessors 

 welcome guests in the nests of their hosts. The appendages, 

 therefore, though now undoubtedly inherited characters, are 

 the specific means by which these inquilines are adapted to 

 their peculiar environment and mode of life among the ter- 

 mites. Moreover, the organs in question not only differ from 

 wings functionally, but, in the adult, they bear no structural 

 resemblance whatever to the wings of flies. Nevertheless, on 

 examining his sections of the above-mentioned specimen, Was- 

 mann found a developmental stage of brief duration during 

 which wing veins appeared in the posterior branches of the 

 embryonic appendages. Now, assuming that Wasmann's 

 technique was faultless, his specimen normal, and his interpre- 

 tation correct, it is rather difficult to avoid his conclusion that 

 we have here, in this transitory larval phase, the last sur- 

 viving vestige of ancestral wings now wholly obliterated from 

 the adult type, that, consequently, this wingless termite guest 

 is genetically related to the winged Diptera, and that we must 

 see in the appendages aboriginal wings diverted from their 

 primitive function and respecialized for the quite different pur- 

 pose of serving as organs of exudation, (cf. "Modern Biology," 

 p. 385.) Indeed, phenomena of this kind seem to admit of 

 no other explanation than the atavistic one. It should be 

 remembered, however, that Wasmann does not appear to have 

 verified the observation in more than one specimen, and that 

 a larger number of representative specimens would have to 

 be accurately sectioned, strained, examined and interpreted, 

 before any reliable conclusion could be drawn.^ 



Such, in its most general aspect, is the atavistic solution 

 of the problem presented by the homology of types. In it, 



^This transitory lymphatic, or tracheal venation appearing in the 

 appendages at the stenogastric stage may not have the particular 

 significance that Father Wasmann assigns. Such venation, even if 

 vestigial and aborted, need not necessarily be a vestige of former 

 toing venation. To demonstrate the validity of the atavistic inter- 

 pretation, ail other possible interpretations would have to be defi- 

 nitively excluded. 



