272 



s. GOTO 



were two other connections besides t!ie one shown in the fi"-iu"e on the 

 left side and seven on the riglit side, making ten in alL In Crihrdla 

 saiujuinolcnta (Figs. 44 & 45) there is an ampulla directly underneath 

 the madreporite on the right side of the median ])lane, C()nnected with 

 tlie ;ixi:il sinus and receiving some of the pore-canals. In Fig. 45 one 

 sees the connection of this ampulla with the axial sinus by means of a 

 solid string of cells. The communication l)etween the two cavities is, 

 however, direct in one of the adjoining sections. The communication 

 passage between the axial sinus and the stone-canal here described, is 

 always on the right side of the median plane, and when single, runs 

 through only a few sections, so that it is perhaps quite natural that 

 the majority of observers have overlooked it. 



We thus see tliat the axial sinus communicates with two cavities, 

 on the aboral side with the stone-canal (as well as the pore-canal), and 

 on the oral side with the circular enteroc(L4 (Fig. 49). It may inci- 

 dentally be remarked that some of the pore-canals open directly into 

 the axial sinus, the case of Cribrella above mentioned being only one 

 particular case among many others. 



I sliall now add a few notes on the histology of the epithelium of 

 the hydro -enterocœl 



The wall of the body-cavities of the bipinnaria consists of a single 

 layer of exceedingly flattened cells whose boundaries can not be recog- 

 nized l)y simple staining with hematoxylin. The protoplasm is 

 finely granular and takes up the stain tolerably well. It secretes on 

 the stn-face turned away from the cavity line muscular fibrils. That 

 these are really muscular I conclude from their optical ])roperties and 

 their behaviour towards stains, which are exactly similar to those of the 

 muscular fibrils of the oesophagus. Most of these mesodermic muscle 

 fi.bres run circularly around the body-cavity, i.e., transversely to the an- 

 tero-posterior axis of the Ijody ; Ijut there are also longitudinal fibres 



