85 
[Packard. 
In Perophora melsheimerii and Lacosoma chirodota all the ab- 
dominal feet bear a complete double circle of crochets, and unlike 
the larvae of Hepialidse and Cossidse, the anal legs also bear a com- 
plete double circle of crochets, as well developed as those of the 
other legs. 
The origin and primitive number of the crochets and morphology of 
the abdominal legs. — Although there may be observers who have no- 
ticed that the abdominal legs of freshly hatched caterpillars have 
less numerous hooks than those of the later stages, I do not know 
that any one has published such observations since the time of 
Lyonnet. In his enduring and classical work above cited, the 
great anatomist states that in the young the number of hooks is 
much’less than in the mature larva. 
My attention was at first directed to this matter while examin- 
ing the abdominal legs of the freshly hatched larvae of Parorgyia 
parallela (FI. i, fig. 1). The membranous anal leg appeared to be 
divided into three segments, which in alcoholic specimens are toler- 
ably persistent, for though there are no definite sutures between 
the sections, the latter are indicated by the arrangement of spinu- 
lated setae, of which there are two groups one on the first and the 
other on the second segment. The third segment is the crochet- 
bearing portion ; it is more or lesseversible, the pedunculate disc-like 
sole or planta being .retracted by two muscles (fig. 3, m) one on 
each side and inserted distally at the base of the crochets or 
hooks. 
But what interested me most was the unexpected bilaterally 
symmetrical structure of the planta. In fig. 1, it will be seen that 
the number of crochets in the newly born caterpillars is only four, 
and this will apply to all the abdominal legs. Moreover, the hooks, 
or crochets, are disposed in two groups, viz., a pair on each side. 
A previously undescribed organ was also noticed ; it is a little bi- 
lobed organ, the free edge of which projects beyond the planta, 
though not so far as the extremities of the hooks. This is what 
we shall hereafter, from its function, call the grypogene, 1 as in it 
are developed the hooks or crochets of later larval life. If then we 
take into account the bilateral disposition ol the two pairs of hooks, 
the bilateral symmetry of the grypogene and the two retractor mus- 
cles of the planta, the view that the membranous legs of caterpil- 
lars show at their extremity a bilateral symmetry, not remotely 
1 Gr. ypvnos, hooked; y even, yeivopiai, to beget, to be the origin. 
