xv, 6 Shaw: Campbellosphaera ^07 



soon as the membrane ceases to conform with the segmentation 

 products of the protoplast, the outer limit is visible only in cases 

 of more or less deeply stained material. Examples of such are 

 found on slides bearing material stained with Bismarck brown 

 alone (Nos. 1 and 3). In the shrunken, Venetian turpentine 

 preparations each gonidium is surrounded by a membrane which 

 has almost no thickness on the outer side, but reaches to the 

 center of the coenobium on the inner side, grading from one side 

 to the other in such a way that the cavity of the coenobium is 

 filled with the substance of these walls, except for very small 

 interstitial spaces where three of the walls meet, and a large 

 space in the anterior quarter of the coenobium. The very thin 

 outer part of the gonidium wall has an extent of about a fourth 

 or fifth of the circumference of the gonidium, and a correspond- 

 ing superficial area of the gonidial protoplast is in close relation- 

 ship with neighboring somatic cells. A large proportion of the 

 shrinkage that occurs in the Venetian turpentine specimens 

 takes place in the gelatinous matrix, if there be such, which 

 fills the coenobial cavity. 



The natural form of the membranes of the gonidial cells is 

 best shown by specimens near the margins of the cover glasses of 

 the type slide and others of the same and sister lots of Venetian 

 turpentine preparations. The marginal and submarginal speci- 

 mens on these slides are swollen instead of shrunken like those 

 which make up the bulk of the preparation. This is true under 

 about the marginal millimeter of the 24 millimeter square covers. 

 The specimens here are beautifully plump. In fact many of 

 them seem to be excessively turgid. The swelling involves only 

 the cell membranes and not the protoplasts. It is most marked 

 at the edge of the cover and in a space the greater part of a 

 millimeter in width. Then, in a narrower zone, the specimens 

 grade off from terete to shrunken. The marginal specimens are 

 also faded. The Bismarck brown is here more rapidly and com- 

 pletely faded than the nigrosin stain, in both the single- and 

 double-stained material. The most beautiful of the specimens 

 are the coenobia in which full expansion of the cell walls has 

 been accompanied by a certain degree of bleaching. In some 

 of these, careful focusing reveals the gonidial membranes. In a 

 coenobium with well-developed gonidia it can be seen that over 

 an area on the outer side of the gonidium its membrane is very 

 thin, as noted in the shrunken specimens, and that on the inner 

 side it is very thick — thicker than in the shrunken specimens — 

 so thick as almost to fill the central cavity of the coenobium and 



