1903.] NATURAL SCIENCES OF PHILADELPHIA. 643 



curved contour, did not fit closely the internal mass of spores, whence 

 the presence of a liquid may be assumed. The ring-shaped pseudocyst 

 presented the same general appearance as the spore mass, and it also 

 appeared to be inclosed by a membrane. The pseudocyst was so 

 dense that the ellipsoidal body could not be seen through it, but a deep 

 furrow could be detected extending around the line of juncture, giving 

 the entire element the optical section seen in fig. 6. The diameter 

 of the sphere formed by the protective membrane was considerably 

 greater, and now measured 750 microns, as against 420 microns when 

 removed from the centipede. 



The next day the cyst had dehisced. It now showed a membranous 

 bag, lying within the disintegrated remains of the pseudocyst. This 

 bag showed two valves, and may be compared with the split shell of a 

 walnut. It was evidently of to\igh consistence, since movements of 

 the cover-glass, while rumpling it considerably, failed to tear it. It 

 was entirely empty, which fact would seem to indicate that the spores 

 are projected from the cyst with some force when dehiscence takes 

 place. 



The mechanics of the process are probably somewhat as follows: 

 The formation of the bulky pseudocyst at one pole causes a gradual 

 weakening of the protective membrane at this pole. In the condition 

 illustrated in fig. 5 the protective coating appears to be reduced to a 

 thin shell enclosing an empty space. This space, however, is doubtless 

 occupied by the substance of the membrane, rendered transparent by 

 the presence of a liberal quantity of water. Eventually the membrane, 

 weakened by the absorption of water, and pressed upon from within 

 by the pseudocyst, yields at the thinnest place and the contained mass 

 is released. Whether the ellipsoidal ])ody splits on account of the 

 opening of the protective membrane, or by means of the liquid which 

 it evidently contains, I do not know. The latter seems to be the more 

 probable reason. 



The annular mass has been termed, and I think correctly, a pseudo- 

 cyst, yet it by no means possesses the .permanent nature which this 

 element sometimes displays. It seems probable that we should find 

 various conditions from a mere residual mass to a definitive pseudo- 

 cyst, since the latter condition is evidently derived from the former. 

 In the case of Acutispora, the condition may probably be regarded as 

 intermediate. The pseudocyst has become more than a mere residuum, 

 but has not acquired the definitiveness it reaches in a genus like Sty- 

 lorhynchus. 



Cnemidospora spiroholi presents the less evolved condition. In this 



