318 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



The second polar body (Bl) and the inner nucleus (A2) of the first polar 

 body now fuse to form the polar nucleus, or the so-called "paranucleus" 

 (Fig. 267, 7iu. p), the outer nucleus (Al) of the first polar body later under- 

 going dissolution. That only two and not all three polar bodies enter into 

 the formation of the polar nucleus (paranucleus) is proved by the fact 



amt 



Fig. 272. Fig. 273. 



Fig. 270. — Litomastix. Eight-cell stage, {amt) Trophamnion. {his) Embryonic 



blastomere. {his. os) Blastomere with oosome. (nw. p) Polar nuclei. 

 Fig. 271. — Litomastix. 14-cell stage, {amt) Trophamnion. {his) Blastomere. {his. os) 



Blastomere with oosome. {nup) Polar nuclei. 

 Fig. 272. — Litomastix. 60-cell stage, {amt) Trophamnion, or polar membrane, {nup) 



Polar nuclei. 



Fig. 273. — Litomastix. 221-cell morula, {amt) Trophamnion. (c) Embryonic cells. 



{csp) Spindle cells, {myc) Mesenchyme cells of host. 



that the diploid number of 16 chromosomes and not the triploid number 

 is present. 



The egg is inseminated by a single sperm, which after having entered 

 the egg loses its tail, only the head being transformed into the male 

 pronucleus (Fig. 267, sp). During the fusion of the male and female 

 pronuclei the oosome moves from its original more or less central position 



