Miscellaneous. '• 483 



or tbui-joiuted, with the free extremity directed towards the e.uidal 

 portion. 



The legs make their appearance under an analogous form, and 

 fold down against the thorax in proportion as they enlarge. Their 

 articulations are at first very indistinct, but soon become more 

 marked ; and we then distinguish all the parts which ordinarily com- 

 pose these appendages. 



The abdomen, which increases more and more in length, gra- 

 dually shows the nine segments with which it is furnished at the 

 time of hatching ; but it is folded in the form of a bow in front of 

 the thorax and cephalic mass, which it finally masks in part. 



The caudal seta), as already stated, originate early upon the last 

 abdominal segment ; but like the other appendages (antenme, man- 

 dibles, raaxillse, legs) they are at first destitute of any segmenta- 

 tion, and, what is more, of all villosity. 



During the whole time that the animal remains in the egg we do 

 not see any internal organ completely formed in it; the intestine 

 itself is onlj^ indicated by a mass of oily drops and vitelline gra- 

 nules occupying the axis of the body, and more or less o])aque 

 except towards the caudal extremity, which is perfectly transparent. 

 It is almost unnecessarj^ to say that the vitellus becomes less and 

 less abundant in proportion as the body and its appendages are de- 

 veloped. As in all other insects, it adheres to the dorsal region, 

 which is always the last to be formed. 



It is to be noted that for a very long time (about two months and 

 a half) all the appendages and, especially, the cephalic mass have 

 so little consistency as to be diluent, after the fashion of sarcode, 

 if the embryo is extracted from the Ggg and immersed in water. 

 By degrees, however, the organs become consolidated, and towards 

 the end of the sixth month, or in the first days of the seventh, the 

 embryo bursts its envelope and exclusion takes place. 



At this moment the j'oung larva of Palinyenia vlrgo is at most 

 1 millim. in length. It is still destitute of some apparatus which, 

 at the first sight, would appear to be indispensable for life, and the 

 late appearance of which may well surprise us. Thus at first it 

 possesses no visible nervous or muscular system, no circulatory ap- 

 paratus, no complete digestive tube, and no special organs of respi- 

 ration. Its mouth is not so well armed and its legs less villous than 

 in the adult lai-va. Its antennte and caudal seta3 possess neither the 

 number of joints nor the villosity which they will afterwards acquire ; 

 in a word, compared with what it will be a little before its nym- 

 phosis, it may be said to be a very incomplete animal. 



We have elsewhere described in detail the singular metamor- 

 phoses that the false branchiaj of Palingeiiia virgo undergo. They 

 appear at first in the form of tubular ca3ca suspended from the pos- 

 terior angles of the first six segments of the abdomen ; then, with 

 increasing complication, they become lamellar, at first simply denti- 

 culated behind, but afterwards furnished with tubidar fringes on the 

 margins ; then they pi'esent definitively the ap[)earancc of a double 

 lanceolate leaf, traversed by a large tracliean trunk with fine 

 branchlets. 



