•);,•> 



Prof, M'lntosli'd Xotes from the 



apparently uniform, ami coutaiu mud rich in organic 

 remains. 



Tiic fornun' or stomachal region enters the followitig or 

 intestinal region by au aperture which is thrust backward as 

 a cone. Moreover, the walls of the organ undergo a struc- 

 tural differeutiatiou, for a short distauce before reaehiug the 

 aperture (text- fig.) they become finely reticulated and dotted 

 as if formed of muscular or erectile tissue {ec), whilst the 

 liniug of the tube consists of the same mucous membrane 

 as in frout. Further, the adjoining circular fold of the 

 diaphragm {sj)t. 3) is provided with a similar, though 

 thinner, layer of the sauie tissue (ec), which likewise 



Longitudinal section of tlie alimentary apparatus at the third septum, 

 spt.S, showing traces of the special uuiscular layer, ec, enveloping 

 the postei'ior wall of the stomach and its sinuses, and continued 

 over the valvular region, vaL ; hp., liypoderm ; coel.c., ccelomic 

 corpuscles ; m^., mucous glands. 



occurs in two of the folds of the organ in front of the 

 foregoing. This tissue is apparently muscular, and its 

 minute structure is interesting as showing the peculiar 

 muscle-cells with their granular contents and nuclei which 

 stud the free border of the muscle. Ziircher ^ has given a 

 good description and figures of the structure of this tissue. 

 It evidently controls not only the wall of the canal but the 

 blood-sinus on its outer surface, and thus may have con- 

 siderable effect on the main trunks proceeding forward 

 to the branchiae. The cadomic corpuscles often form a 



* Op. cit. p. 203, and fig.«. 33 & 35. 



I 



