578 



THE AMERICAN NATURALIST 



[Vol. XL 



ner). At an early period the two lateral folds are formed and are 

 marked off in the embryo by a lateral furrow whieli is wanting in 

 the adult, or is apparent in certain places only (Kiikenthal). The 

 side folds, which at first conver«re dorsallv in the enibrvo, later 

 become parallel, and finally in the adult become divero-ci'it above, 

 ^rhe .urowth in b.vadtli of the middle area is corres|)ondingly 

 (greater in its upper than in its lower portion. The two ))osterior 

 limitino- folds of th<- middle area a{)j)ear to be formed later. They 

 are fiirured by Kiikenthal from an eml)ryo 102 em. long. In the 

 embryo the Mirfacc of tlir MioiU i. nuirked oif into little spaces with 

 a beautiful n-ularit> and from th<- c<Mitcr of (>ach knob-like space 



in the embryo is not ureatly .litferent frl)m that of tlie adult. 



A .hort .iiMance above the .nout are the blowlu.lcs. The.se are 

 tu<. ahn<..i circular openings, dose together and directed ..bli<,nely 

 upward and forward on the muzzle. Owen cliaracterizes their 



