ON THE AGAMIC REPRODUCTION AND MORPHOLOGY OF APHIS 77 
the amnion and the allantois, are, I believe, structures without a 
representative in the other two sub-kingdoms. 
There is perhaps, as Zaddach maintains, a certain analogy between 
the primitive segments of the Articulate animal and the primitive 
vertebrae (“ Urwirbel” of Remak) in the Vertebrate, but with the 
commencing differentiation into tissues the resemblance entirely 
ceases. The appendages of the Vertebrate embryo are more Mol- 
luscan than Articulate in their primitive mode of development. Not- 
withstanding all these great and real differences, however, there 
appears to me to be one respect in which a most singular analogy 
obtains between the Vertebrate and the Articulate type :—it is in the 
construction of the head. 
Adopting, in some respects, the views of Professor Goodsir, I can 
recognize at least six more or less complete segments in the com- 
pletely ossified Vertebrate cranium. It is clear that the Vertebrate 
mouth opens like that of the Articulate animal, though on the opposite 
side of the body, between an anterior and a posterior set of cephalic 
segments. In the interior of the cranium a no less natural boundary 
between the anterior and the posterior set of cephalic segments is 
afforded by the pituitary body and its fossa, when the latter enists. 
I find, again, in the cranio-facial bend of the base of the cranium 
in the Vertebrate embryo, something wonderfully similar to the 
cephalic flexure of the Articulate head, and in the cranial trabecule 
(Schadel-balken of Rathke), analogues of the procephalic lobes. 
While fully recognizing the fundamental differences between the 
Articulate and the Vertebrate type, then, I think we should greatly 
err if we overlooked such singular analogies as these. Future re- 
search will show whether they are or are not the outward signs of a 
deeper internal harmony than has yet been discerned, between the 
Articulata and Vertebrata. 
Since the present memoir was read to the Society, some additional 
facts of importance have come to my knowledge. In the first place, 
my friend Mr. Lubbock, having undertaken to work out the develop- 
ment of Coccus, was led thereby to search for what I have called 
“ovarian glands” in other insects. His results will be published at 
length elsewhere; but he permits me to say that corresponding 
organs exist in all Lepidoptera, Hymenoptera, Geodephagous and Hy- 
drodephagous Coleoptera, Diptera, and most iVeuroptera, while they 
are absent in Orthoptera, Pulex, Libellulida, &c., and are all terminal, 
instead of forming groups between the egg-germs, in the non- 
1 As expressed in the Edinburgh New Philosophical Journal, 1857, p. 118 ef seg. 
