302 Mr. J. S. Bowerbank on the Structure 



The one whicli I am about to describe was found in a large 

 muddy ditch, which is on the left hand of the foot-path from 

 Tenby to Finally, South Wales. It is of an oval form, and rarely 

 exceeds half an inch in length from one extremity of the fibre to 

 the other, and the central case is about four lines long. The 

 fibres are of a greenish amber colour, the case partaking of the 

 same hue, but much deepened by its greater degree of density. 

 PI. XVIII. fig. 2. represents a specimen of rather more than the 

 average size. When carefully denuded of the surrounding fibre, 

 the case is found to be divided into numerous nearly equal-sized 

 polygonal areas, which are most frequently five- or six-sided. 

 These are produced by a raised network of fibrous structure, 

 partly imbedded in the surface. From the angles of these reti- 

 culations the surrounding open fibrous structure springs, which 

 preserves the same form of reticulation as that of the parent sur- 

 face. Fl. XVIII. fig. I. represents the same specimen as figure 2, 

 but magnified ten diameters. 



The case has frequently a deep sinus which extends entirely 

 across it, causing it to assume very much the same form as a 

 short, swollen grain of wheat, as represented by figure 4 ; and 

 under these circumstances the mammse are found opposed to each 

 other in the direction of, what is then, the short axis of the case, 

 and are situated just without the outer edge of the sinus. When 

 there is no depression of this body, the mammae are found op- 

 posed to each other at the ends of the cocoon, as represented by 

 Fl. XVIII. fig. 3. 



The sinus is produced by a partial state of collapse of the body 

 of the cocoon, caused apparently by the gradual diminution of its 

 gelatinous contents. 



The cocoon in almost every specimen that I have opened was 

 found to contain a dense opaline gelatinous matter. When re- 

 moved it readily separates in water into flaky masses, which, when 

 viewed by transmitted light with a power of 500 linear, appeared 

 to be composed of exceedingly minute granules. 



Upon carefully examining the gelatinous contents of several 

 specimens which I opened, I found in two of them small vesi- 

 cular bodies, which have every appearance of being the eggs or 

 embryos of the animal. In the gelatinous matter of one speci- 

 men I found ten of these bodies, and in another six of them, ap- 

 parently in difiierent stages of development. They are usually 

 pyriform, and have frequently a deposit of minute, dark, granu- 

 lated matter towards the smaller end. In both cases in which these 

 bodies occurred, they were found in greater quantities at one end 

 of the cocoon than at the other. Fl. XVIII. fig. 7. represents one 

 of the best-developed of these embryos by transmitted light and 

 a power of 300 linear. The network which covers the outer sur- 



