TRANSMISSIBILITY OF FUNCTIONAL MODIFICATIONS 



91 



consists not merely in the fact that the ovarian-tubes and ovum- 

 primordia remain small, but also in a diminution of the TiVAnher 

 of ovarian-tubes (Fig. 105) ; the workers have always fewer ovarian- 

 tubes tlian the females of the same species, and — what is of especial 

 importance — the reduction in the number of ovarian-tubes has been 

 effected to a different extent in different species of ants. In the red 

 wood-ant [Formica rufa) the workers still possess from twelve to 

 sixteen ovarian-tubes ; in the meadow-ant (Formica pratensis) only 

 eight, six, or four; in Lasius fuliginosus there are usually only 

 two (one on either side) ; and in the little turf-ant {Tetravioriwin 

 ccespltum) there are none 

 at all. We have here, there- 

 fore, a phylogenetic process 

 of degeneration, which has 

 reached different degrees 

 in the different species, and 

 has only been completed 

 in one (TetramoriuTii). The 

 case stands as I previously 

 stated it: 'The elimination 

 of a typical organ is not 

 an ontogenetic process, but 

 a phylogenetic one,' it de- 

 pends not upon ' the mere 

 influences of nutrition 

 which affect the develop- 

 ment of the individual, but 

 always on variations in the 

 germ-plasm, which, to all 



appearance, can only come about in the course of a long series of 

 generations ^. 



Against this proposition an observation by O. voni Rath has 

 been cited. According to it, three drone larvse which had been 

 accidentally fed by the workers with royal food exhibited striking 

 retrogressive peculiarities in their sexual organs. The testes contained 

 only immature sperms (just before emergence from the pupa), and 

 the copulatory organ was entirely wanting. That a certain degree 

 of fatty degeneration of the testes should be caused by the ' unusual 

 fattening' is not surprising, but it seems to me very questionable 

 whether the absence of the copulatory organ can be referred to 

 the abnormal diet ; it ought to be definitely decided, by the investiga- 

 * Aeussere Einjlilsse als Entwickelungsreise, Jena, 1894. 



Fig. 105. Ovary of a fertile Queen-Ant and 

 ovaries of a Worker. Od, oviduct. A, one ovary 

 of Myrmica kevinodis with many ovarian-tubes, 

 in each of which there is an almost ripe egg 

 {Ei) and a younger egg {Ei'). B, the ovaries of a 

 Worker of Lasius fuliginosus ; each ovary has only 

 one ovarian-tube, and no ripening egg-cells. After 

 Elizabeth Bickford. 



