A ' \SE OF YOLK FORMATION NOT rnNNKiTED 

 WITH IHI-: PRODUCTION < >F OVA. 



OSCAR RIDDLE. 



Tli.- -i-crclion or production of true yolk in situati. >n- other 

 th. in in ova or in the follicular cells which surround ova is nt 

 kiniuii so far as I am aware. 'Nurse" or "yolk" cell- have of 

 course long been known to exist in several group- .'I animal-; 

 the-e. however, are evidently the equivalents of follicular cell- 

 IT ol ova. It is therefore of some interest to record tin- lindin^ 

 ol i rue \olk in spaces within the connective tissues which lie 

 i AN TH. illy to the follicular membrane of capsule- \\hirh had 

 pn-\ ion-Iv liberated ova. 



I hese observations were made on the ovaries of the rinnion 

 fowl during the mid -summer season. During Jul) and .\umi-t ot 

 i In- ] in -i nt summer the writer had occasion to examine tin 

 ovaries t more than one hundred full-grown hens. Aimm^ ilu--e 

 iln i. \\ en- at least six or eight ovaries which showed unmi-takablv 

 iln- peculiar accumulation and jJacement of yolk \\hich i- In M 

 dr-t i il ii -d. 



In oidi-r to be Mire that one is really di-.ilin- \\iih "extra- 

 o\ ul.ti " .md "extra-follicular" formation of yolk, and not nuT.-K 

 \\iili ,i mas(|ue of its usual source, it was i r\ \ deiermine 



three things concerning the capsules within \\hich the \.>lk in 

 (|iif-iiou \\as found: (i) That an egg had been -mvly de\-i-lope<l 

 ami liberated from this capsule. (2) That tin- >pa<v in \\hich 

 tin- \ oik was found is quite separate and remo\ ( -d troin tin- space 

 lornuTK' occupied by the ovum, and like\\i~.- n nio\td from tin- 

 lollicnlar cells which surrounded the o\nin. ; I li.u ih 

 cumulated substance is true yolk. I belit-\e that tin- material 

 1 lia\ e i-xamined has enabled me satisfactorily to dcii-nnine each 



ol these points. 



The evidence that the yolk-containing capsiilc-> in .|iu-.tion 

 had prc-vioii-lv borne and liberated ova rests partially upon the 

 finding of capMilc^ showing all the intermediate stages between 



107 



