47 



in Rhodites and Biorhha aptcra {Cynipidcc) the first cleavage- 

 nucleus divides at first into nuclei which shift apart in the direction 

 of the longitudinal axis of the tgg, and, according to their position, 

 are known as the anterior and posterior "pole nuclei." While the 

 anterior nucleus remains inactive for some time, the posterior, by a 

 kind of budding (?), gives rise to numerous nuclei, which take part 

 in the formation of the blastoderm. The anterior nucleus, on the 

 contrary, after the completion of the blastoderm, is said to produce 

 by division the nuclei of the so-called inner germ-cells or yolk-cells."* 

 In the case of Camponotus, however, the anterior cells go to mal-ce 

 up at least the greater part of the blastoderm. 



In the next stage I have, (marked one day old,) the nucleated 

 masses of protoplasm are beginning to arrange themselves in a regu- 

 lar layer in the yolk just a little distance in from the peripheral pro- 

 toplasm (Figure 5). This layer is more regular and the nuclei are 

 more numerous in the anterior than in the posterior half of the tgg\ 

 furthermore, the nuclei lie nearer the periphery. There are still a 

 great many nuclei scattered indiscriminately through the central por- 

 tion of the yolk. Division seems to be going on much more rapidly 

 in the anterior half, and many karyokinetic figures can be seen, some- 

 times six or eight in the same section. 



In a stage a few hours later the nuclei at the anterior end have 

 migrated outward until they form a loose layer in the peripheral 

 protoplasm. Towards the posterior end the nuclei do not divide so 

 rapidly and do not reach the peripheral protoplasm as soon as at the 

 anterior end, so that a longitudinal section of this stage has the ap- 

 pearance shown in Plate II, Figure 6. Figure 7 shows a section 

 through the peripheral layer of protoplasm at the anterior end parallel 

 with the surface. 



FORMATION OF THE BLASTODERM 



By the time the nuclei have reached the periphery at the posterior 

 end of the tgg the layer of protoplasm in the anterior half has be- 

 come divided by deep fissures, running in from the outside, into 

 columnar cells, each cell containing one nucleus. The nucleus has 

 in each case migrated outward to the extreme distal end of the cell. 

 These cells are not formed, however, over the entire surface. They 

 form a cap over the anterior end, and extend on the ventral surface, 

 backward, atout half-way to the posterior end. The dorsal half of 



♦Quoted from Korschelt aud Heider ('99, p. 264). 



