PHRYXIDI. 139 



stages to be compressed or omitted altogether. He concludes, from 

 a study of the larvae of hippophaes and gal/it, that the Phryxid 

 ring-spots first originated on the segment bearing the caudal horn, 

 and that they were then gradually transferred as secondary spots to 

 the preceding segments. 



Weismann argues (loc. cit., p. 228) that there is a fundamental 

 difference between the development of the markings in Eumorphid and 

 Phryxid larvae. In the former the formation of the eye-spots proceeds 

 from a subdorsal line, but they first appear on two of the front segments, 

 and are then transferred to the posterior segments. In the latter, on 

 the other hand, a single ring-spot is formed on the penultimate * 

 segment bearing the caudal horn, and this is repeated on the 

 anterior segments by secondary transference. With respect to the 

 origin of the ring-spots also, there is a distinction between the Phryxids 

 and Eumorphids, inasmuch as the first step towards the eye-formation 

 in the latter consists in the separation of a curved portion of the sub- 

 dorsal line, whilst, in the former, the nuclear spot first seems to originate, 

 and the separation of the mirror-spot from the subdorsal line appears 



to occur secondarily In the Eumorphids, also, the 



formation of the primary eye-spots appears to differ from that of 

 the secondary — in the latter the black " ground-area ;; first appears, 

 and in the former the " mirror-spot." The secondary eye-spots 

 certainly remain rudimentary in this group, so that the evidence in sup- 

 port of this conclusion is thus much weakened. As a final result, Weis- 

 mann advances the opinion that the Phryxids dealt with have reached 

 five different phyletic stages, and that their very different external ap- 

 pearance is explained by their different phyletic ages, and he says that 

 the appearance, from such different larvae, of moths so extremely similar, 

 can otherwise be scarcely understood. He urges that the variations which 

 occasionally occur in the larvae furnish, to a certain extent, a proof of 

 the correctness of the theoretical interpretation offered. Thus, forms 

 reverting to an earlier phyletic stage occasionally occur, e.g., traces 

 of the subdorsal line in the adult larvae of euphorbiae, as illustrated 

 in one of Hiibner's figures, marked as an " aberration," a similar 

 specimen also being in the Staudinger coll., whilst in adult larvae of 

 vespertilio this line appears more frequently, and Staudinger ob- 

 serves that, among several hundred adult larvae of dahlii found in 

 Sardinia, there were some which did not possess a distinct sub- 

 dorsal line, but, in place thereof, and, as its last indication, a feeble light 

 stripe, whilst one showed also a distinct line between the closed 

 eye-spots. As might be expected, a larva in any ontogenetic stage 

 most readily reverts to the preceding phyletic stage, so that those 

 characters present in the preceding stage are those that most com- 

 monly arise by reversion. Larvae of enphorbiae in the last stadium 

 frequently take on the 6th (with a single row of ring-spots) instead 

 of the 7th (with a double row of ring-spots) phyletic stage, whilst 

 reversions to the 5th phyletic stage (a single row of ring-spots 

 with connecting subdorsal line) are very rare. These larvae which, 

 in the adult instar, belong to the 6th phyletic stage, not infrequently 

 show the characters of the 5th stage more or less developed, e.g., 

 vespertilio. 



* Weismann calls the 8th abdominal the " penultimate " segment throughout 

 his descriptions. 



