78 



M. F. GUYER AND E. A. SMITH 



In making the precipitin tests the lenses were taken from four 

 individuals of each species of mice to be tested, ground up in a 

 mortar and diluted with 3 cc. of normal salt solution. The mix- 

 ture was then filtered and to the resulting fluid 1 5 drops of fowl 

 serum, sensitized as in table 3 with lens of Peromyscus mani- 

 culatus gambeli, were added. In the case of Peromyscus cali- 

 fornicus insignis, which is much larger than other members of 



TABLE 4 



SPECIES OF MOUSE TESTED 



PRECIPITATION AFTER EIGHTEEN HOURS 



Serum of Fowl B. May 4. 



Peromyscus maniculatus gambeli 

 Peromyscus californicus insignis 

 Peromyscus eremicus fraterculus 

 Perognathus fallax fallax 



Abundant 



Nearly one-half that of 1 



Very slightly more than that of 2 



None 



Serum of Fowl C. May 9 



1. Peromyscus maniculatus gambeli 



2. Peromyscus eremicus fraterculus 



3. Peromyscus maniculatus sonoriensis 



4. Peromyscus maniculatus rubidus 



5. Perognathus fallax fallax 



Abundant 



About one-half that of 1 



Almost as abundant as 1 



Very slightly less than 3 



None 



the genus, four young individuals of about the size of adult 

 P. gambeli were selected, because it was desired to have the 

 amount of lens material used in each species as nearly the same 

 as possible. After eighteen hours any precipitate that had ap- 

 peared was concentrated in a centrifuge in order to get a more 

 accurate estimate of the relative quantities formed. 



It will be observed from table 4 that all species of the genus 

 Peromyscus gave positive precipitin tests to serum sensitized 



