elegant net-work of sarcode with wide oval and round 
_ meshes radiating irregularly from a central point. 
q I had supposed. 
The 
membrane is traversed by irregularly radiating ridges 
of firmer substance, which unite in the centre in a 
projecting boss at the point where, in this specimen, the 
glass-rope” has unfortunately been torn out. 
WYVILLE THOMSON 
(To be continued.) 
THE ANCESTRY OF INSECTS 
WA ERIN a very few days after my last article on the 
Y  Orizin and Metamorphoses of Insects” appeared 
i. Nature, I received from Mr.’ Packard a memoir,* 
under the above title, in which he developes his latest 
views on the same subject; and I.am happy to find 
that his views do not differ so much from mine as 
He lays great stress, as is natural, 
on the larval forms. “If we compare,” he says, “ these 
early stages of mites and myriopods, and those of the 
true six-footed insects, as in the larval Meloé, Cicada, 
Thrips, and D:agon-fly, we shall see quite plainly that 
they all share a common form. What does this mean? 
To the systematist who concerns himself with the classi- 
fication of the myriads of different insects now living, it 
is a relief to find that all can be reduced to the compara- 
tively simple forms sketched above. It is to him a proof 
_ of the unity of organisation pervading the world of insects. 
He sees how Nature, seizing upon this archetypal form 
has, by simple modifications ot parts here and there, by 
the addition of wings and other organs wanting in these 
simple creatures, rung numberless changes in this elemen- 
talform.” And again (p. 151), ‘‘ Going back to the larval 
period, and studying the insect in the egg, we find that 
nearly all the insects -yet observed agree most strikingly 
in their mode of growth, so that, for instance, the earlier 
stages of the germ of a bee, fly, or beetle, bear a remark- 
able resemblance to each other, and suggest again, more 
forcibly than when we examine the larval condition, that 
a commondesign or pattern pervades all.” 
He distinguishes, as in his previous writings (p. 175), 
two principal types of larva :— 
“There are two forms of insectean larve which are 
pretty constant. One we call leptiform, from its general 
resemblance to the larvze of the mites (Leptus). The larvze 
of all the Neuroptera, except those of the Phryganeidze 
and Panorpidz (which are cylindrical, and resemble cater- 
pillars), are more or less leptiform, z.¢., have a flattened 
or oval body, with long thoracic legs. Such are the larvae 
of the Orthoptera and Hemiptera, and the Coleoptera 
(except the Curculionidz ; pos-ibly the Cerambycidze and 
Buprestidz, which approach the maggot-like form of the 
larvee of weevils). On the other hand, taking the cater- 
pillar or bee larvae, with their cylindrical fleshy bodies, in 
most respects typical of larval forms of the Hymenoptera, 
Lepidoptera, and Diptera, as the type of the eruciform 
larva,” &c. 
At first sight it would appear that Mr. Packard’s con- 
clusions differ widely from those which I have advocated. 
He rejects, indeed, the suggestion made by Haeckel that 
the “ common stem form of all Tracheata” may be found 
in “Zoeaform Crustacea.” Itis evident, he says (p. 159), 
that “the Leptus fundamentally differs from the Nauplius 
and begins life ona higher plane. We reject, therefore, 
the crustacean origin of the insects.” And elsewhere 
“we find through the researches of Messrs, Hartt and 
Scudder that there were highly-developed insects, such as 
may-flies, grasshoppers, &c., in the Devonian rocks of 
New Brunswick, leading us to expect the discovery of 
low insects even in the Upper Silurian rocks. At any 
rate this discovery pushes back the origin of insects 
beyond a time when there were true Zoéz, as the shrimps 
* Being a chapter from ‘Our Common Insects,” by A. S, Packard, jun. 
(Printed in advance.) 
and other allies are not actually known to exist so far 
back as the Silurian, not having as yet been found below 
the coal-measures.” 
But then he observes that the “larvae of the earliest 
insects were probably leptiform, and the eruciform con- 
dition is consequently an acquired one, as suggested by 
Fritz Miilller.” Again, “for reasons which we will not 
pause here to discuss, we have always regarded the eruci- 
form type of larva as the highest. That it is the result 
of degradation from the Leptus or Campodea form, we 
should be unwilling to admit.” And once more, “ The 
Caterpillar is a later production than the young, wingless 
Cockroach.” J 
Mr, Packard had already expressed these opinions else- 
where, and as I have on the contrary suggested that the 
grublike, or Lindia-forms were the first to come into exist- 
ence, then the Tardigrade-form, and lastly, the Campodea- 
form, I had supposed that our views were in direct opposi- 
tion to oneanother : but I am glad to find from other pass- 
ages that after all there is not so much dfference as these 
passages would seem to indicate. I cannot, indeed, agree 
with him in his classification of Insect larvze ; he ranks 
the Caterpillars with the grubs and magyots of Bees and 
Flies, as a class for which he proposes the term “ eruci- 
form” in opposition to the “ leptiform” larvae of Orthop- 
tera, Hemiptera, and most Coleoptera. It seems to me, 
on the contrary, that the two great groups are the 
Hexapod or Campodea-form, and the apod, grublike 
type, which I have proposed to call the Lindia-form. At 
the first glance, no doubt, the heavy sluggish Caterpillar 
seems to have more in common with the grub of a 
Bee than with the active larve of Coleoptera. The dif- 
ference, however, is one of habit, not of type. 
As regards the ancestral forms of Insects, Mr. Packard 
considers that “while the Poduras (p. 154) may be said to 
form a specialised type, the Bristle-tails (Lepzsma, ATa- 
chilis, Nicolitea, and Campodea) are, as we have seen, 
much more highly organised, and form a generalised or 
comprehensive type. They resemble, in their general 
form, the larvee of Ephemerids, and perhaps more closely 
the immature Perla, and also the wingless Cockroaches. 
Now such forms as these Thysanura, together with the 
mites and singular Pauropus, we cannot avoid suspecting 
to have been among the earliest to appear upon the 
earth ; and putting together the facts, first, of their low 
organisation, secondly, of their comprehensive structure, 
resembling the larvz of other insects, and thirdly, of 
their probable great antiquity, we naturally look to them 
as being related in form to what we may conceive to have 
been the ancestor of the class of insects. Not that the 
animals mentioned above were the actual ancestors, but 
that certain insects bearing a greater resemblance to 
them than any others with which we are acquainted, and 
belonging possibly to families and orders now extinct were 
the prototypes and progenitors of the insects now known.” 
As regards the probable origin of this Leptus form, 
Mr, Packard’s views are expressed in the following pas- 
sage (p. 169) :—‘ While the Crustacea may have resulted 
from a series of prototypes leading up from the Rotifers, 
it is barely possible that one of these creatures may have 
given rise to a form resulting in two series of beings, one 
leading to the Leptus form, the other to the Nauplius. 
For the true Annelides (Chztopods) are too circumscribed 
and homogeneous a group to allow us to look to them for 
the ancestral forms of insects. But that the insects may 
have descended from some low worms is not improbable, 
when we reflect that the Syllis and allied genera of Anne- 
lides bear appendages consisting of numerous joints ; 
indeed, the strange Dwujardinia rotifera, figured by 
Quatrefages, in its general form is remarkably like the 
larva of Chloéon.” , 
Moreover, though Mr. Packard says that “the caterpillar 
is a later production than the young wingless, cock- 
roach,” he elsewhere (p. 182) says, “it is evident that in the 
