Morphology and Phylogeny of Insects. 437 



regarded as secondary forms wliicli arc derivable from the 

 primary Campodea-YikQ, larva and have arisen by the process 

 of adaptation. The theory started by Braucr was supported 

 by Packard * and Lubbock f, and has been the generally 

 accepted one hitlierto. At the time when Brauer published 

 his little paper, which has met with so much success, our 

 knowledge of the embryonic development of insects was still 

 very scanty, since Kowalevsky's :j: memoir, by which new 

 paths were opened out, and Butschli's§ paper, in which the 

 presence in an insect embryo of numerous abdominal appen- 

 dages was asserted for the first time, were not published until 

 1871 and 1870 respectively. This, as it seems to me, 

 explains the favourable reception of Brauer's hypothesis, with 

 which, as I shall show, the embryological facts are decidedly 

 at variance. That this hypothesis has hitherto maintained 

 its importance for the majority of zoologists and is constantly 

 repeated in text-books is in my opinion accounted for by the 

 insufficiency of the embryological statements on the question, 

 as also by the fact that certain valuable papers are incom- 

 pletely known ; thus, for instance, Tichorairow's memoir 

 upon Bomhyx mori^ because it is written in Russian, has only 

 become more fully known to foreign students within the last 

 few years. But although I will not deny that the embryology 

 of Insects, and of Lepidoptera in particular, still requires 

 completion, nevertheless I venture to assert that precisely on 

 the subject of the abdominal appendages our knowledge is 

 already satisfactory. The facts bearing upon this were 

 communicated by Kowalevsky, Tichomirow, and Graber. 

 Kowalevsky, who, inter alia^ investigated the embryology of 

 Srnerinthus ijopuli, figures ten pairs of perfectly distinct abdo- 

 minal appendages upon the germinal streak of this moth. 

 Tichomirow describes and figures in Bomhyx mori small but 

 " distinct " appendages on all the abdominal segments with 

 the exception of the first ; in subsequent stages (when the 

 cephalic segments become fused together) only the appen- 

 dages of the third to the sixth segments and of the eleventh 

 segment (which afterwards fuses with the tenth and ninth) 

 are preserved and undergo fuither development, while the 



* Tackard, ' The Ancestry of Insects ' (Salem, 1873). 



t Lubbock, ' Urspruug u. Metamorphoseu der Insekten ' (Jena, 1876). 

 [' On the Origin and Metamorphoses of Insects ' (Loudon, Macmillau and 

 Co., 188;3).] 



\ A. Kowalevsky, " Embryologische Studien an Wiirmern und Arthro- 

 podeu," M^m. Ac. Sc. Petersb. 7, xvi. no. '2, 1871, 70 pp., 12 plates. 



§ Biitschli, " Zur Eutwicklungsgeschichto der Biene," Zeitsclir. f. wiss. 

 Zool. Bd. 20, 1870, pp.519-5Li4, 4 plates. 



