EARLY DEVELOPMENT OF GRAFFILLA. 183 



It i- necessary to mention only briefly the manner in which 

 the "o\ ulation" takes place. By the time the absorption of 

 yolk ha- reached the point seen in the case of tin- <>\ a on the ridit 

 of Fig. 9 the formative capsule may be -aid to be practically 

 independent of any ovarian connections, and it only remains for 

 the cap-ule to be freed from the vitellarium. Ilo\\e\er, its 

 aM.nlinient with the yolk glands per-i-t- f.-r some time after 

 thi-. even indeed until the two eggs reorganized, if reorganization 

 i- IM-I essary. In Fig. 10 is a capsule just about ivadv to be set 

 free into tin- parenchyma; most of the yolk cell- ha\<- \ieldcd 

 11 1 > i heir I'ooii i ntents to the capsule, and the region immediately 

 -in roimdin- its upper margin shows only delicate -trand- con- 

 ii \\ith a few of the remaining nurse- cell-. Shortly 

 in.: this period tin- strands are severed and the capsule 

 round- up. and as the whole structure is pu-hed about in the 

 parent h\ ma by the movements of the mother \\onn ill 



Illldel w . i ( |e\ eli ipmellt . 



I p io ihe present we have been using the term "capsule" to 

 mean the \\hole yolk mass surrounding the t\v<> eggs; and \\e 

 mu-i now consider brielly the formation of the thin cap-ule <T 

 -In II, 1 iv \\ hich we mean the membrane containing the i u ciliated 

 embryos ! the later stages. Since the eggs with their illicular 

 la\i i ..t \olk do not enter the uterus, it is not probable that an\ 

 ol i In- - , reiioiis from the unicellular shell-gland- reach the 

 and thu- lake part in the formation of the -hell, as mt ur- in 

 the i ase "I "\ i | i.i rous forms. I have not followed all <>t the -tep- 

 in the li.nnalioii of the shell, but it has been ob-er\ed that a- 

 dexelopmeiu proceeds the outermost layer of the \.>lk, \\hich .it 

 lii-t i- very plastic and yields readily to any ob-tnn i ii.n in the 

 pareiich\ma. gradually becomes more re-i-iant. linally taking 

 on (he thin elastic character met with in all of the advanced 

 stages. It is probable that the shell is in part the product of 

 the parenchyma. 



It remain- to say a word about the "rcorgani/ation " of cells 

 in those cases in which the membrane in part or completely 

 di-appears from the two ova. Kven in the extreme cases it is 

 doubtful whether the cytoplasmic part of the cell becomes in- 

 di-criminaicly a ociated with the yolk portion of the cap-ule. 



