

228 MKKISTIO VARIATION. [I'AKT I. 



towards ili.- ri-ht np ]i.-r canine. The whole .anterior part of the lower 

 jaw is thus twisted ;i little towards the left side. 



these two ili -finite cases of absence of incisors, in the following instances 

 the, , |,n -imii'tiun thiit the absence was due to variation, but a definite state- 



niciit I'iinii'it In- made. 



H. smithii: milv four incisors in lower jaw, B. M., 148."), a. H. gracilia : 

 doul.tnil ease of absence of -- <>n both sides. B. M., 7*9, l>. H. nyuia : doukt'ul if 

 ri^rlit '- lias been present. B. M. 



Anterior Premolars. 



In tin- great majority of both Asiatic and African species of Her- 

 bhe ant. -i in) premolar (//) is normally present in both jaws, and 

 in these species '' <-ases of absent y were seen. When present it 

 i> a tooth of small but still considerable size. It appeared from 

 tin- specimens that / in the species //. yracilis (Africa generally), 

 and IK. tli i ' and y , ! in //. ijalura (E. Africa) are commonly absent. As 

 in other cases ft' ali.M-nce nf ti-i-th tin- ijuestion arises whether the 

 absence is due t<> age or accident, or on the other hand to original 

 deticiencv. This question cannot be definitely answered, but some 

 considerations touching it should be mentioned. 



First, as has been said, the tnoth when present is of moderate size: 

 though small, it is ijuite large enough to be functional, and is in no 



e rudimentary. In his synopsis of the genera, THOMAS* says of 

 Hi I'IH *tes, " Premolars [ (if only 3 in either jaw, a diastema always 

 present)." There is however no reason for supposing that the presence 

 or absence dt' //' is d. termined by chance. From the fact that a tooth 

 is small, it bv no means follows that it is often lost. To any one 

 handling large numbers of skulls, instances of the contrary must lie 

 familiar. A case in the Otters well illustrates this point. In Lutra 

 riili/u t-i* upper />' i- a small toot h. and from its singular position internal 

 to the canine, it might be supposed that the development of the canine 

 might easily push it out; yet in 41 skulls of Lutra vulgaris, only 

 I case of absence of p_' was seen. Of L. cinerea on the contraiy six 

 skulls are without 7^ ; but as in two young skulls it is present on 

 both side-, then- is thus a strong presumption that in this species the 

 tooth is lost with maturity. The frequent absence in the one species 

 and the constant presence in the others points to a difference in 

 organi/ation li.-i \\een them. When //' is missing in a skull, though we 

 an- not entitled to infer that it has not been present, still the fact of 

 its pr.-M-iH-e in one case and of its absence in another is on the face of 

 it an indication that liet ween the two there is a difference or Variation, 

 but whether tin- Variation lay in the number of teeth originally 

 formed or in the mode in which they were affected by subsequent growl h 

 i- im.-.-rtain. In the specimens to be described the absence of ]> l in 

 certain individuals or species is no less detinite than its presence in the 

 others, and that which i^ a variation in one species will be seen to be 

 the rule iii others. 



A regards the presence of y/' the specimens thus make a progress! ve 

 series. .M,,st species ha\ing /.}, but //.'. as ,-i variation; //. i/rai-ifi'n (and 



O i 



ha\ing /^ normally, but j>\ as a variation and p- 



3 3 

 1 TiK'Mv-., ()., on til.- African Mungooses, 1'. '/.. \., lss-_>, p. 62. 



