608 Dr. A. Arnback-Cliristie-Linde on the 



subject pf dispute. Some authors are of opinion that there 

 is no such dentition, e. g. Leche *, Avho, having raicroscoj)i- 

 cally examined several foetal stages without finding any trace 

 of milk-teeth, comes to the conclusion that the Soricidse 

 have only one dentition. 



Woodward (/. c) is the first who has found rudiments of 

 real milk-teeth in Sorex, the calcified " milk-teeth/' the 

 existence of which Owen f and Tauber J have stated, being 

 the cusps of the permanent teeth. 



The question whether a milk-dentition exists or not is 

 thus decided. However, 1 hope that the result of my investi- 

 gation may be of some interest, as Woodward has examined 

 only one stage of Sorex and observed only a few uncalcified 

 rudiments. 



The upper jaw. 

 Foetus: hodij -length about 11 mm. 



The first labial growth of the tooth-band met with is 

 related to the rudimentary I-^ and is thus Id-. It is a highly 

 vestigial structure, as might be expected (PI. XVIII. fig. 1 ; 

 text-fig. 2). 



All the functional antemolar teeth with the exception 

 of the large I^ have predecessors in the milk-dentition 

 (PI. XYIII. fig. 1). Besides, I have found a predecessor 

 of the rudimentary C (text-fig. 3). 



The milk-dentition in the upper jaw thus consists of Id-, 

 Ids Id-', Cd, Pd\ Pd-, Pd^ Pd^ Id^ Cd, and Pd-' are repre- 

 sented by highly vestigial minute buds, and Id' by a compa- 

 ratively large labial outgrowth from the tooth-band. 



The otlier milk-teeth arc cup-shaped. 



One of the most interesting points in connection with I' 

 is the fact that the tooth-band here gives rise to three out- 

 growths from the same })oint, representing three dentiticyps. 

 The lingual one (1'') developing to a permanent tooth, the 

 labial ones must be traces of older dentitions, i. e. of the 

 lacteal and prelaeteal dentitions (PI. XVIII. fig. 1, PL). 



Also in Erinaceus eiiropceus on the labial side of the corre- 

 sponding functional tooth — P — there are traces of two 

 dentitions, as appears from Lcche's figures (/. c. Taf. vi. 

 figs. 37-40). Leche, having overlooked this fact, mentions 



* Leclic, W., " Zur Eiitwickhiupsireschichte des Zabnsvstems der 



Saugetiere," Teil i., Bibl. Zool. (Stuttgart, 1805). 



t U\veii,R., ' Odontographio," i. iV: ii. (London, 1840-45y 



X Tauber, P., " Oni Tandsaet olt Leveiuaade bos de danske Flagermuus 



og lusektfedere," Naturbistorisk Tidskrif t, Bd. viii. (I87i'-7y). 



