88 GEORGO ORIHAY SHINJI 



produces, by rapid multiplication, all of the embryonic cells. 

 As stated above, the first cleavage products of our scale insects 

 do not behave in this way, but both cleavage cells continue 

 multiplying, and some of their products later form the blasto- 

 derm, while the others remain in the interior of the egg and 

 constitute the so-called yolk-cells. In this respect, the develop- 

 ment of the eggs of coccids resembles that of the silkworm and of 

 Neophylex and Gryllotalpa, studied, respectively, by Toyahaa 

 ('02), Patten ('84), and Korotneff ('84). Silvestri ('H) recently 

 discovered that in a parasitic Hymenopteran, Copidosoma, one 

 of the two nucleoli escapes from the nucleus at the end of the 

 growth period of the oocyte. Later, this escaped nucleolus 

 passes into one of the two cleavage cells. During a series of 

 cleavage processes, only one cell remains in possession of this 

 nucleolar substance and becomes the germ cell. In another 

 parasitic Hymenopteran the escaped nucleolar bodies become 

 localized at the posterior end of the egg imtil one of the first 

 cleavage cells reaches out and takes them up into its protoplasm. 

 In both cases the cell which becomes possessed of this escaped 

 nucleolar substance, differentiates into the germ cells. 



In the scale insects I have studied no escape of the nucleolar 

 substance into the egg was observed and the germ cells do not 

 appear during the cleavage period. 



All cleavage cells divide mitotically. No case of amitotis, as 

 described for Blatta by Wheeler ('93), has been observed. The 

 fact that very many cells are in the process of division during 

 the early stages indicates the rapidity with which cells divide. 

 Nelson ('15) states that no case of a single spireme stage was 

 found in the cleavage cells of the honey-bee. On this point my 

 specimens agree strictly with his observation. An abundance of 

 spireme figures are, however, found among the blastoderm cells. 

 As the number of cleavage cells increase, they migrate, one by 

 one, toward the periphery and become imbedded in a thick 

 cortical layer of the protoplasm. In figure 44 the condition of a 

 loose blastoderm is shown. Although the cells are arranged in a 

 peripheral layer, they are very far apart from one another. The 

 spaces between these blastoderm cells are gradually filled by the 



