Allen, Association in the Guinea Pig. 301 



behavior which develop shortly after birth with the perfection 

 of the muscular coordination, may be termed "deferred char- 

 acteristics." 



Individual differences in habitual behavior of the guinea 

 pig may be considered either as intelligent adaptations, or as 

 accidental variations ; probably when these slight modifications 

 are analysed, the more tenable view will be that the majority of 

 the individual characteristics are variations. Individual charac- 

 teristics show themselves in rapidity of movement, habitual ac- 

 tivity, tameness, adaptability to changing situations, and in such 

 habits as climbing, gritting the teeth, squealing, etc. 



Certain characteristics become modified and altered as time 

 goes on. One group of guinea pigs at first chuckled a great 

 deal, the cause of which I am unable to state. Appar- 

 ently the noise was made by the rapid gritting of the 

 teeth. One individual would begin it and immediately every 

 guinea pig in the room would take it up and continue for half a 

 minute or more. Within three months this habit was discon- 

 tinued almost entirely. 



In its diet the guinea pig resembles the rabbit. It is vora- 

 cious and will gnaw almost anything in the vegetable kingdom. 

 Its foods in the laboratory are carrots, oats, hay, grass, lettuce 

 and parsnips. It gnaws constantly, the wire, the floor, the par- 

 tion, anything within reach. In this, too. it resembles the rab- 

 bit. Its manner of eating and of searching for food would lead 

 one to the conclusion that it is a grazing animal in its natural 

 habitat. 



The guinea pig bears constantly, and is quite prolific in 

 confinement. The average number in a litter is two, though 

 litters of one or three occur frequently. The period of gesta- 

 tion is from 65 to 69 days, and the young are weaned about 

 the end of the second week. Growth is retarded by birth for 2 to 

 5 days. From 5 days to 12 months there is a steady increase in 

 weight. The age of sexual maturity is extremely variable, but 

 seems to be about four months.' 



' MiNOT. Senescence and Rejuvenation First Paper : On the Weight of 

 Guinea Pigs. Jour, of Physiol., Vol. XII, p. 97, 1891. 



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