48 



subsequently; and probably sooner, these larvge had all become sta- 

 tionary, and never moved afterwards from the point in the bark to 

 which they had attached themselves. At this date, they presented 

 imder the lens the appearance of conspicuous, flat, white scales, oval 

 and one-third longer than broad, their long diameter being now about 

 equal to one-third of the extreme transverse diameter of the old 

 scales. The white appearance of these larva? I found to be due to a 

 white powdery secretion from the general surface of their bodies; 

 Avhich being removed by a moist caraei"s-hair pencil, their bodies re- 

 assumed their original pale yellow color. As with the larvae of many 

 other Bark-lice and some Plant-lice, there were, in addition to this 

 powdery secretion, threads of exceedingly fine, hair-like, cottony floss 

 irregularly attached to them, and evidently secreted from the gen- 

 eral surface of their bodies. At this period they could without much 

 difficulty be detached from the bark by a moist camel's-hair pencil; 

 but already they had lost almost all appearance of organization. Their 

 legs, which only seven days before were distintitly articulated and as 

 large comparatively as in ordinary insects, and which then discharged 

 all the functions of locomotion with ease, were now almost entirely 

 obsolete ; so that even on holding the insect up to the light, under the 

 most powerful Stanhope and Coddington lenses, but the faintest traces 

 of legs could be perceived. Their antennae had now disappeared alto- 

 gether. As to any organized beak, I could discover nothing of the 

 kind ; but not improbably it might have been inserted in the bark 

 and broken off short by detaching the insect from that bark. Motion 

 in this creature there was none whatever; and but for having seen 

 them crawl about with ease only seven days before, and knowing that 

 in the course of two or three months almost every one of these appar- 

 ently inanimate scales would generate scores of living white eggs, I 

 should never have supposed them to be living animals. On the pre- 

 ceding day, i. e., only six days after the general hatch, I had closely 

 examined dozens of them, and could not perceive that a single one 

 moved in any way. According to Dr. Mygatt, who says that his 

 trees were watched closely by the members of his family, the first- 

 bark-louse seen to hatch out was on the 23d of May; and after the 

 27th not one was seen to move. So that the process of degradation, 

 by* which the animal loses all its locomotive and sensorial organs, 

 probably commences about three days after the hatch, and is almost 

 completely consummated in the space of four days. 



, Agassiz lays it down as a universal rule, that "the earliest con- 

 dition of an animal cannot be its highest condition — it does not pass 

 from a more perfect to a less perfect state of existence." {Methods 



