Till-: VA'Al: INTERNAL C1IANGP:S. 5 



its ai)iH"ai-aiice in fVoin two to tour days after deposition, or in from one- 

 third to one-seventli of the total duration of the enil)ryonic life. In Eury- 

 nnis [.hih)dioc aehange was first noticed in forty two liours after deposition, 

 so that the first stage occupied about one third of its hfe. In Cercyonis 

 ah)pe no difference was noted until the third or fourth day or after one 

 seventh of its (nal existence had elapsed. 



The first chano-e of color proclaims the advent of the srroinf jxriof/, m 

 which a uniform alteration is noticed in every part of the contents ()f the 

 e<rir,_p,-()l)ahly the period known to eml)ryoh)gists as that in which the 

 formation of the blastoderm or cellular layer takes place ; it is indicated 

 externally either by a uniform dotting of the whole surface with spec-ks of 

 a deeper, usually reddish, color giving to the egg a new tint ; or by a 

 simple change of color, its cause being obscure. In Cercyonis aloi)e for 

 exami)le, the color changes from honey yelhnv to a pale pink color ; in 

 Kuphydryas phaeton (64:87) * the original yellow becomes strongly tinged 

 with brown ; in Eurynms philodice the yellow yields to a pale salmon ; in 

 Limochores taumas the change is from pale green to a pale wood-brown 

 tinged with green ; in the last case a closer inspection shows this alteration 

 to be acc(Mnpanied by the appearance of deep vinous flecks scattered over 

 the whole c<^g ; sometimes these are reduced to mere dots, at others they 

 are larger, while ill-defined streaks are distributed over the surface with 

 great irregularity and no apparent meaning. This period is of even shorter 

 duration than the preceding. In Eurymus philodice it lasts but fourteen 

 hours ; in Limochores taumas four or five days ; but the usual term is one 

 or two days. In Ancyloxypha numitor, the first two stages occupy two 



days and a half. 



The f/iird period is first indicated l)y a decided and significant change 

 in the distribution of the spots or of the tints. Either there is simply a 

 distinction between the poles, or more commonly, an aggregation of the 

 flecks into larger more or less irregular spots, forming a narrower or broader 

 band around the middle of the egg, at equal distances fi-om the base. Dur- 

 ing this period, which doubtless corresponds to the formation of the germinal 

 band, the organs and parts of the future caterpillar, whether they are in 

 their primordial condition or have assumed the contour and divisions of the 

 growing insect, lie Avholly in an annulus upon the same plane with the base 

 of the Qgg ; this seems almost impossible in the elongated fusiform egg of 

 Eurymus philodice, but I see no reason, from the observations I have 

 made, to believe that this embryo departs in any way from the general law. 

 This period is generally longer than any of the others, occupying in nearly 

 all the species I have observed fully one half of their embryonic life ; in 

 Limochores taumas, however, it occupies but two or three days of the 

 twelve or thirteen usually passed in the egg. In Euphydryas phaeton the 

 * Black faced mnnerals refer to the plate ; others to the figures on the plate. 



