C26 FOOT AND STROBELL. [Vol. XVII. 



Crampton (6) has applied Miescher's interesting artificial 

 digestion experiments to the egg of Molgula, with a view 

 to sustaining his conclusion that the yolk-nucleus owes its 

 origin to albuminous granules within the nucleus. " In order 

 to place beyond question the identification of the yolk-matrix 

 and nuclear granules as the only purely albuminous constitu- 

 ents of the cell at this stage, artificial digestion was resorted 

 to," p. 38; "it seems an almost unavoidable conclusion that 

 the nuclear granules are either solid masses which pass out 

 from the nucleus to form the yolk-matrix, or they are semi- 

 fluid albuminous substances which are able to pass readily 

 out through the nuclear wall, and which in preserved material 

 are coagulated by the fixing reagents," p. 40. 



We have applied this method of artificial digestion to the 

 yolk-nucleus in Allolobophora, but in spite of repeated trials 

 we have been unable to obtain the results Crampton gets in 

 Molgula.i The yolk-nucleus in Allolobophora is especially 

 favorable for these experiments, for it stains intensely with 

 iron-haematoxylin, and its presence can be demonstrated as 

 long as any trace of the substance is left in the cell. 



The ovaries were fixed in corrosive sublimate, sectioned 

 (5 n) and fastened to the slide with the hot-water method. 

 Before placing them in the digestion fluid they were immersed 

 for thirty minutes in a dilute solution of iodine, in order to 

 remove all trace of corrosive sublimate. Experiment proved 

 this to be a necessary precaution, for the sections not treated 

 by the iodine showed no response to the pepsin, even after 

 six hours' immersion. While in the digestion fluid the tem- 

 perature was kept at 40° C. by means of the water bath.^ 



After examining several preparations before and after diges- 

 tion, we were convinced of the inconstancy of the action of the 



arising from the same substance as archoplasm." Wilson {31), p. I2i : "Foot 

 maintains that the yolk-nucleus in Allolobophora is not of nuclear but of 

 ' archoplasmic ' origin, though no relation between it and an attraction sphere 

 is established." • 



1 We used " Pure Golden Scale Pepsin," manufactured by the New York and 

 Chicago Chemical Company, following the formula given by Crampton (1% pepsin 

 in 1/5% HCl). 



2 We are greatly indebted to Dr. R. W. Tower for kindly directing these 

 experiments. 



