372 Dr. G. Biitschli on the Gastrea- Theory. 
small (generally elongate) marks, which are finely punc- 
tured, and generally filled with yellow pollen. The under 
flanks of the prothorax, the sides of the metasternum, the 
metathoracic epipleura, and the sides of the basal segment of 
the abdomen are not densely and finely punctured as they are 
in C. gigas. 
Hab. Queensland. 
Erotylide. 
Aulacochilus humeralis, n. sp. 
Ovate, very convex, shining, black. Hach elytron with 
two large yellow spots, the basal one occupying all the 
shoulder, nearly touching the scutellum, but leaving the 
narrow reflexed lateral margin black; the spot is oblique on 
its inner margin and trisinuate posteriorly. The second spot 
is behind the middle, transverse, lunate. ‘The head is very 
distinctly and moderately thickly punctured. The thorax is 
narrowed in front, finely but distinctly and moderately closely 
punctured. ‘The sides are rather straight (as compared with 
allied species), the margins strongly incrassate ; the incrassate 
margin much wider at the anterior angles; the anterior angles 
rather prominent. The elytra are very delicately striate- 
punctate, the intervals obscurely punctured. Length 44 lines. 
Hab. Pasamanca, Philippine Islands (‘ Challenger’ Haped.). 
This species is allied to A. guadrisignatus ; but is quite 
black, more convex, the thorax straighter at the sides, with 
more incrassate lateral margins, and the humeral spot of the 
elytra does not leave a black spot on the callus. 
British Museum, South Kensington. 
XLUI.—Remarks on the Gastrea- Theory. 
By G. BurscuHi *. 
[Plate XV. ] 
In the sphere of speculation on the Metazoa as regards their 
developmental history and phylogenesis the explanation of the 
probable origin of the primitive bilamellar form has hitherto 
formed a principal difficulty. Hence, of course, the concep- 
tion which one must form of the general morphology of this 
first bilamellar Metazoan form has also varied. 
* Translated by W. 8. Dallas, F.L.S., from the ‘ Morphologisches 
Jahrbuch’ (1884), Band ix. pp. 415 427, 
