262 s. GOTO; 



opeiiiuii' of the pore-cutial, aii<l makes an obtuse aiio-le with the latter. 

 The wliole lengtli of the canal is, however, inconsiderable. 



In staii'e E the rudiments of tlie arms have become very marked, 

 and witli them also the diverticula of the secondary left posterior 

 enterocœl, which enter them. The latter, wdiich in the mean time, 

 has been thorouo-hly separated from the anterior enterocœl, has extend- 

 ed t(.i the right side on the ventral, as well as on the dorsal, region ; the 

 whole forming, if we leave out of consideration the five diverticula of 

 thearms, a, thick horse-shoe shape, embracing about three-fourths of the 

 stomach on the left side. We must also remember that at this stage 

 the aboral disc is inchned to the sagittal plane at an angle of about 

 70° ; and conse(pient.Iy the plane of the horse-shoe formed by the secon- 

 dary left posteri(n- enterocœl makes ne;irly the same angle with the 

 Ion«' axis of the larva. It must be remai-ked here that the secondary 

 left posterior enterocœl is not vet separated from the anterior enteroc(el 

 of the right side, for from Fig. 12, it might [)erha[)s be inferred tliatit is. 



The epigastric enteroccel has become very nearly circular and has, 

 at the same time, beüiin to send out diverticula, into the arms, there 

 being, in this stage however, only four diverticula (Fig. 12). 



The periœso[)hage;d enteroc<eI is nearly in the same condition in 

 which it was in st:ige D ; only it has grown more around tlie stomach, 

 encirclinu" about half its circumference, its dorsal end remaining- all t!ie 

 time nearly at the same |)oint. 



There is no change in the stone-canal worth noting, it having 

 simply incre.ised in length slightly. The plane containing the 

 h^^di'ocœlic pouches has, liowever, become inclined to the sagittal plane, 

 but it makes with it a smaller angle than the aboral disc. 



Stage F (Fig. lo) is a very interesting one: the aboral disc has 

 assumed its definitive position, making a right angle with the sagittal 

 plane, but the prnsoral {)ortion of the body and especi;dlv the three 



