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 csecal 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 bine 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 larvae, 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 larvse 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 noxious 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 healthy maturity of the larva, being attained, the development of the canal is then 

 completed. 



PART I. CHALCIDID^. 



The two species I am about to describe are parasites in the nests of the wild-bee, Antho- 

 phora retusa. They seem to differ in their particular economy as in generic character. 



The first species is generically distinct, so far as I am able to ascertain, from any hitherto 

 described genus ; the other is a species of Monodontomerus, which may prove to be iden- 

 tical with a known species, but of which there is some doubt ; so that the name which I 

 propose for it must be regarded as provisional. 



