32 Miss J. E. Lane-Claypon. On the Origin, etc., of [June 16, 



plant residues are converted by bacterial action in the soil into calcium 

 carbonate. 



(5) The return of base by the growth of plants and the production of 

 calcium carbonate by the decay of plant residues are sufficient to maintain 

 soils neutral which are poor in calcium carbonate, and to replace the bases 

 which have been consumed in nitrification and similar changes. 



On the Origin and Life History of the Interstitial Cells of the 

 Ovary in the Rabbit. 

 By Janet E. Lane-Claypon. 



(From the Physiological Laboratory, University College. Communicated by 

 Professor E. H. Starling, F.E.S. Eeceived June 16, 1905.) 



[Plate 1.] 



The majority of the investigators of the subject consider that the cells of 

 the germinal epithelium arise by differentiation of the peritoneum, and 

 become embedded in the subjacent mesoblast, there being probably a dual 

 process, namely, the downgrowth of the cells themselves and a simultaneous 

 upgrowth of the subjacent mesoblast. 



The fate of the cells thus embedded has given rise to much discussion. 

 All observers agree in stating that they give rise to the ova, and most 

 observers consider that they give rise also to the follicle cells ; but de 

 Foulis (8),* Schron (16), and Wendeler (20), believe these cells to be derived 

 from the connective tissue. 



Pfliiger (15) and Waldeyer (18), although differing in regard to the develop- 

 ment of the ovary, both consider that the germinal cells give rise to the 

 cells of the follicular epithelium, there being most probably a previous division 

 of the original cells. 



Nagel (14) also agrees that the follicle cells are derived from the germinal 

 epithelium. Balfour (4) believed that some of the cells of the egg-clusters 

 became ova by differentiation, and he described besides a number of small 

 cells, of which some formed the follicular epithelium and the others probably 

 either served as foodstuff for the rest, or eventually themselves formed ova or 

 follicle cells. 



Buh 1 r(7) c -scribes the formation of the follicular epithelium by the 

 * Th se numbers refer to the entries in the bibliography at end. a 



