MONOGRAPH OF THE NORTH AMERICAN PROCTOTRYPID^. 19 



Both authors may be cou- 



of (Ecanthus n'lreus and its Parasite Teleas. 

 suited to the advautage of the studeut. 



lu lieu of origiual work of this kind I have deemed it advisable to 

 reproduce here a summary of Gauiu's work, by Balfour, together with 

 his figures, in order to illustrate the remarkable changes the embryo- 

 larva must undergo before assuming the normal larval stage. 



Balfour says: 



The very first stages arc unfortunately but imperfectly known, and the interpre- 

 tations offered by Ganiii do n<.t in all cases appear .,uite satisfactory. lu the 

 earliest stage after being laid the egg is inclosed in a capsule produced into a 

 stalk (Fig. 1, A). In the interior of the egg there soon appears a single spherical 

 body, regarded by Ganin as a cell (Fig. 1, B). lu the next stage three similar bodies 

 appear in the vitellus, no doubt derived from the first oue (Fig. 1, C). The central one 

 presents somewhat different characters to the two others, and, according to Gauiii 

 gives rise to the whole embryo. The two peripheral bodies increase bv divisiou and 

 soon appear as nuclei imbedded in a layer of protoplasm (Fig 1 I) E F) ' The 

 layer so formed serves as a covering for the embryo, regarded by Ganin as equiValent 



E.G. l.-En.b.-yonk, .levolopnMnt „r i,latyga..ter: A, eg.; B, primitive cell; C, additional cells de- 

 veloped from tl>e Inst; 1) and K, further cellular development; F, final embryonic stage. (After 

 Gaum.) "^ ^ \^»i/oi 



to the amnion ( ? serous membran.-) of other insect embryos. In the embryo cell new 

 cells are stated to be formed by a process of endogenous cell formation (Fig 1 D 

 E). It appears probable that Ganin has mistaken nuclei for cells in the earlier stages' 

 and that a blastoderm is formed as in other insects, and that this becomes divided 

 m a way not explained into a superficial layer which gives rise to the serous en- 

 velope and a deeper layer Avhich forms the embryo. However this may be, a difter- 

 entiatiou into an epiblastic layer of columnar cells and a hypoblastic layer of more 

 rounded cells soon becomes apparent in the body of the embryo. Subsequently to 

 this the embryo grows rapidly, till by a deep transverse constriction on the ventral 

 surface it becomes divided into an anterior cephalothoracic portion and a posterior 

 caudal portion (Fig. F). The cephalotlmrax grows in breadth, and near its an- 

 terior end an invagination appears, which gives rise to the mouth and resophagus 

 On the ventral side of the cephalothorax there is first formed a pair of claw-like 

 appendages on each side of the mouth, then a posterior pair of appendages near the 

 junction of the cephalothorax and abdomen, and lastly a pair of short conical an- 

 tenna^ in front. 



At the same time the hind end of the abdomen becomes bifid, and gives rise to a 

 fork-like caudal appendage; and at a slightly later period four grooves make their 



