1880.] 



ARRANGEMENT OP THE MAMMALIA. 65.') 



tS'ilT^lZ^- ""> ' V'-' \' ^'^' "' t'^^ Marsupialia. Among 

 existing Rodents, in fact, all conditions of the milk-dentition exist 



(,as in the Kabbit') to none at all. 



The same thing is observed in the Insectivora, where the Hed-e- 

 og and probably CenMes, have a full set of milk-teeth, .-^^111 

 ave yet been found in the Shrews. In these cases it is obvious hat 



tltrtt T] 1'' Ff "'•"7 '^^^" ^^^PP^^^^^d in the more modi- 



the eSl m1 f r^'' ''"7 '^"^ ^^ "° ^^^^^-"^'^ doubt that 

 rW.-r f ^l^'^."P'^'s liave undergone a like suppression of the 



^7^:::^^J^ir'' -' '''' ^-^-^^^^''-^ —^ 



r^et^^TiZ f 'if "°- ^^^''''P'^\ possesses an unmodified pentadactyle 

 pe.. It the hallux is present, it presents an extensive movement in 

 adduction and abduction; in fact, the pes is prehensile. Th i^ 



hStf^ A ' ^"'^'"-'i^ present the same type of pes, with the 

 hallux reduced or suppressed. Hence, considering the relations of the 



fhTtT/lVf ?■' ^.^'•--^^■^^- -"'^ the Phalangers, it seems 1 kely 

 n wblh } 1"'^ '" '^T' S'""P' '^ '-^^^^ ^ r^d«e«l P'-'-hensile pes^ 



Ke wio , f'H ^ 'Pf'"' T^^^'^''''' °^ '^' ^''' "0"^ characteriz 

 Th- 11 e^'stiug Marsupialia. 



ihirdly, the most marked peculiarities of the reproductive organs 

 and processes m the Marsupial are in no wise transitio^nal, but i^s nlu 



ot the root of the penis is unlike any arrangement in the higher 

 mammals ; and the development of the-bulb and of Cowper' dand 



IZT- °^ "''^' '^"?° '^'''''''^' ^" ^'^^'- I'^ 'J^« fenfale, the cyst 

 me Ira is as completely separated from the vagina as it is in' the 



3h ;i . '°f''^r'^^ ^Pe"«l peculiarity which leads from 

 lather than towards, the higher mammals. In a Monotreme Tii 

 fact, the anterior end of the genito-urinarv passage exhibiStwo 

 very shor dilatations or cornua, one on eaahlide."Lr,^e Middle 

 Ine, a little distance behind these, the ureters open on a p imminent 



betw Jhe '"P- 'V ^^'' "'^T^'S '^ '^'' bladder^Iies in frJnt o a "d 

 be ow the genital cornua. Now, if we compare this arran-emeit 

 with that which obtains in the lower forms of the higher Smali" 

 we find that the ureteric papilla have separated ateralTy and 

 moved forwards, in such a manner as to occupy the base of the 



S r ad';;;hem" 'iTn "'''"" ^^"^ '' ''' '^''^^'^ -'i ---ha 



possess, in ac clition two anterior upper and two ower deciduous incisor. 

 Bo hare simple conical teeth, the sacs of which are merely en dXci,1ke 

 gum The upper is no more than one hundredth of an inch Ion. tit ower 

 rather ai-gcT. It would be interesting to examine foetal Guinea-,^>s in rehtTon 

 to his point ; at present thej are known to possess only the hindmost dccihous 

 molars, and, so far, agree with the Marsupials. ' """'""sr ciccicluous 



