356 Studies in the Theory of Descent. 



logical tree based on the supposition that it is the 

 rows of spots which have been inherited in cases 

 where they occur, and not the mere tendency to 

 their production by the transference of the one 

 originally inherited primary spot to the remaining 

 segments, the attempt will fail. The greater 

 number of the species would have to be arranged 

 in one row, since one species always bears a per- 

 fected form of marking, which appears in the young 

 stages of the following species. But it is very 

 improbable that nine different species, derived 

 directly the one from the other, would contempora- 

 neously survive. 2 One species, D. Vespertilio, 

 could not be inserted at all in the genealogical 

 tree, since it wants one character which occurs in 

 all the other species, viz., the caudal horn, which 

 is absent even in the third stage, and must there- 

 fore have been lost at a very early period of the 

 phyletic development, so that we may consider it 

 to be on this account genetically allied to the 

 oldest known form. But the markings of this 

 larva pass through precisely the same stages of 

 development as do those of the other species. 

 Now if the ring-spots were inherited as such, the 

 existence of a hornless species with ring-spots 

 would be an insoluble riddle, and would favour the 

 admission of parallel developmental series, which 



* [See Darwin's remarks on the struggle for life being most 

 severe between individuals and varieties of the same species 

 " Origin of Species," 6th ed. p, 59. R.M.] 



