184 EMBEYOLOGY OF THE LOWER VEETEBRATES CH. 



explained as a repetition of an ancestral condition in which the 

 intestine as a whole was long and spirally coiled. 



An important feature of such ;i spiral coiling of the gut rudiment 

 is that it would ii"cess,n ily tend to bring about a twisting of the 



..-V 



\'i'.. ]();,. hi-,-, ti<,i,> ,,f yoiiii- L.-pi.Iosiivns ! lUges -TJ A , :;f, ( H), M (C), ami 37 

 Irom tin- ventral side to show tin- modelling of the inti-stiiir. 



g.b, jjall-I'lu.l.lei-: //, liv.-r: I', v.-nti i.-l,-. 



.iliiii.-ritai y i-aiial just, in front of the spirally coiled port,in in a 

 counter-clockwise direction as seen I'mm behind, *.. a movement in 



which points n 1 he ventral side nf t.he aliinentai-y canal would 



[lifted towards I In- ri^lil side. A- already indiealed such 



atwistm-j"! thU region o|' |h<- alini.-iilary canal ad ually docs lake 



