62 MR. NEWPORT ON THE ANATOMY AND DEVELOPMENT 
powers of the system are most energetic, and when nearly the whole of the food is appro- 
priated to the enlargement of the body. Very little undigested substance then remains, 
after the assimilation of the nourishment imbibed, and consequently no excretory outlet 
to the organ is required. But when the assimilation of food begins to be arrested, and 
the rapidity of growth is diminished, as is the case when the larva is approaching its 
maturity,—changes which seem to lead to the inference, that the forces of combination in 
the primary organisms of the body become less and less energetic in proportion to the 
degree of stimulus to which they are submitted,—the digestive apparatus then assumes a 
new form: it is narrowed and elongated, and being connected with a column of granu- 
lated cell-masses, which, derived originally from the yolk, are continuous with those that 
constitute the walls of the digestive cavity at one end, and at the other with the tegu- 
ment, the czecal extremity of the sac becomes perforated, and the cells separating in the 
axis of the column form a tube, that is quickly lined with epithelial membrane, to allow 
the passage of the refuse of digestion, the tegument having previously separated also at a 
given point, by which an excretory or anal outlet to the canal is completed. The mate- 
rial first removed is composed chiefly of disintegrated epithelial cells, which line the digest- 
ive cavity, and are thrown off as they become aged and worn-out, during the elaboration of 
nutrient fluid, like the cells which form the cast layers of tegument. This change of struc- : 
ture does not take place in any of the parasitic larvee, so far as I am aware, until the indi- 
vidual is replete with nourishment, and ceases to feed, preparatory to more extensive alter- 
ations of form. When this marked period of its existence has arrived, it is first necessary 
that the unassimilated portions of food, together with the worn-out materials of the body, 
should be removed, and this necessitates the change from a closed receptacle to a canal. 
But further reason for this late completion of the organ, as well in those larv which are 
confined to a given space with their food, and in those still more confined between the 
tissues of other insects, at once suggests itself. In the one case the food stored up must 
remain pure and uncontaminated, for the support of the larva preyed upon; in the other, 
the fluids of the victim must not be changed from nutrient to rioxious aliment by the 
engenderment of disease within it, through contact with effete matter from the body of 
the parasite, and thus destroy what otherwise it would nourish. But the primary object, 
the ur maturity of the larva, being attained, the development of the canal is then 
completed. 
/ 
PART I. CHALCIDIDA. 
The two species I am about to describe are parasites in the nests of the wild-bee, Antho- 
The first z : Ps ir particular economy as in generic character. 
| st species is generically distinct, so far as I am able to ascertain, from any hitherto 
