ZOOLOGY. 185 
itate our thought and study ; and that, to use Spencer’s words, 
“we cannot, by any logical dichotomies, accurately express rela- 
tions which, in nature, graduate into each other insensibly,’ the 
difference of opinion becomes intelligible; and for my part I adopt 
that system which appears most natural, and which best promotes 
the object in view. It is essentially that of Westwood, given in 
his ‘Introduction,’ which has justly been called the entomologist’s 
bible.” Perhaps this language conveys the idea that I believe we 
have made no advance beyond Westwood’s classification; but if 
so, it belies my meaning, and I have simply been unfortunate in 
expression! And as facts never become obsolete, and the *‘ In- 
troduction” referred to contains more facts, and fewer theories 
and speculations than many later published entomological works, 
I do not think it undeserving the homage paid to it, though it be 
‘in many respects obsolete in 1873.” 
:` (6) Ihave already answered the inquiry, in my feeble way, in 
the above extract: and as to my opinion of the value of embryo- 
logical data in classification, I shall content myself, at present, 
with adducing in its support the opinion of one who is infinitely 
better qualified to form an opinion which has weight. After re- 
ferring in his last annual address, before the London Entomo- 
logical Society, to Packard’s ‘‘Memoir on the Embryology of 
Chrysopa, and its Bearings on the Classification of the Neurop- 
tera,” and to the opinions arrived at by the author, Westwood 
concludes as follows: —‘‘And thus the position of the animal in 
the ovum is allowed to unite into one group Libellula with its 
active, and Hemerobius with its necromorphous pupa; and to 
separate widely Hemerobius and Phryganea, hoth with inactive 
pupa, which are, however, furnished with jaws of a structure, per 
se, for biting a hole in the cocoon before arriving at) the fully- 
developed imago state. I confess that this specimen of classifica- 
tion founded upon embryological data does not carry to my mind 
conviction of its superior worth.” 
~ _The accompanying figure (117) represents the male of the apple bark 
louse, which Riley calls Mytilaspis pomicorticis, regarding it as distinct 
_ from the A. pomorum Bouché of Europe, from the fact that the eggs of the 
. European species are reddish-brown, while those of our species are white. 
-Care should here be taken in ascertaining how soon after being laid the 
eggs are observed, as they may vary in color with the age of the embryo 
within. Certainly we have been unable to detect any difference between 
the bark 1 u of the apple aswe | e obse d it in Jena, Germany, and 
WO uar 
` 
