DEVELOPMENT OP TRICHOGRAMMA EVANESUENS. 183 
divided among the large cells at the posterior pole, which are 
the germ cells. 
(3) In the single case found there were two polar bodies. 
(4) The blastula is fairly normal except for the curious 
arrangement of the chromatin in the somatic nuclei. 
(5) Many nucleoli are cast out into the centre of the egg, 
where they collect till from twenty-five to fifty are present; 
the mass is then extruded on the periphery of the egg. 
(6) As the blastoderm grows it broadens without lengthen- 
ing up to the stage where the germ layers begin to form. 
(7) About thirty-five nuclei sink inwards from the dorsal 
surface of the embryo to form endoderm. 
(8) From the blastoderm stage to that of the gastrula no 
nuclear division appears to take place. 
(9) Shortly after the formation of the endoderm amitosis 
may be found, and from this onwards the number of nuclei 
increases. 
(10) The mesoderm seems to be formed from peripheral 
nuclei, which sink in sporadically; no somites can be made 
out, nor does any segmental method of formation of the 
mesoderm occur. 
(11) The nervous system, stomodaeum, and probably procto- 
dasum, are normally formed. 
(12) The germ cells lie in a pocket formedjby several somatic 
cells, which embrace them. 
(13) Ordinary mouth parts, tracheae, heart, and oesophageal 
valve are wanting ; the head has two horn-like mandibular 
processes, which may assist in scooping forwards the food. 
(14) The larva does not feed on the food little by little, 
defecating as it eats ; instead, it begins by swallowing all the 
yolk at once, so that its body becomes enormously distended 
and stretched. 
(15) Metameric external segmentation is absent, the body 
and head being continuous and sac-like. 
