of these families to be the same as those of the genera. The arrangement of the cells constituting the corpus adiposum, the relative size of the males, and the position of the vulva, will probably, however, be found somewhat variable, and are perhaps characters of not more than generic importance; in which case the arrangement of the nervous system, the presence or absence of an œsophagus, the presence of a single or double ovary, and the development of the young, will, with the absence of the anus, remain as the principal family characters.
I shall endeavour to get some humble bees in the course of this winter, in order if possible to determine some of the many points which yet remain to be ascertained; and I should feel very grateful to any one who would send me even a single specimen of any species of Bombus between the months of December and April. In the meantime, Sphærularia still remains, as it was when Diesing wrote the "Systema Helminthum," a "genus inquirendum."
DESCRIPTION OF PLATE I.
1. Sphærularia bombi x 15. A. Small male.
2. Part of corpus adiposum x 10.
3. Free end of ovary x 250.
4. Two young eggs with rachis x 250.
5. Portion of ovary x 250.
6. Outline of young x 60.
7. Outline of male (?) x 60.
8. Head of male x 60.
9. Tail of do. do.
10. Ovary x
11. Egg, showing the commencement of segmentation, x 250.
12. Do., in a more advanced stage, x 60.
13. Young egg, still more advanced, x 250.
14. Place of union of male and female x 250. a. Part of the body of male. b. Part of skin of female, c. Projection of male fitting into sac-like depression of female.
In the eyes of those who look without prejudice on the theory of descent with modification, the tracing out of homologies has, in recent times, been invested with a new interest. On this theory, the comparative anatomist no longer, in following out the homological relations of parts and organs, pursues an object, captivating, but fruitless, as fascinating as the solving of a puzzle, but barren as to general results.
