164 



ANIMAL AGGREGATIONS 



TABLE Will— Continued 



Culture No. 



No. of Animals 

 Introduced 



No. after 24 

 Hours 



Ratio 



Ratio per Single 

 Original Animal 



Normal Hay Infusion; Parent Culture 48 Hours Old — Continued 



Normal Hay Infusion; Parent Culture 72 Hours Old 



Normal Hay Infusion; Parent Culture Age not Given 



224A. 



22SA. 



24/ 



1:3 



1:1.5 



they cannot be so easily dismissed. As will appear shortly, I hold no 

 brief for the allelocatalysis theory as stated by Robertson; but it is 

 only fair to note, as Robertson himself states (1927), that in order to 

 be closely comparable, experiments such as these must have the 

 same history and be run at the same time, a fact well known to 

 experimental workers in this and other related fields of physiological 

 zoology. It is therefore hardly fair criticism to compare a single 

 allelocatalysis experiment run at one time with another run later. 

 Fortunately, we do have a statistical method of analysis which takes 

 into consideration the biological sensitiveness of paired experiments, 

 that is, "Student's" method (Student, 1925; Fisher, 1925). Applying 



