4 22 Campbell ’ — Studies on the 
calls this the endospore, apparently overlooking the develop- 
ment of the true cellulose endospore which arises later in 
contact with the protoplast. She also mentions a layer 
(mesospore) between the two thick layers (exospore and 
mesospore of Fitting), but no evidence of such a membrane 
was found in Kraussiana which agrees essentially with 
S. Helvetica as described and figured by Fitting. The 
principal difference lay in the mesospore being thinner than in 
that species, and remaining more nearly of the same thickness 
in the earlier and later stages ; thus indicating that its increase 
in size in the late stages was due to actual growth, and not to 
mere stretching. 
Between the protoplast and the mesospore and between 
the latter and the exospore the space is filled with what 
appears to be a fluid, doubtless containing plastic material 
derived from the tapetum. In all the preparations examined, 
this substance appeared perfectly homogeneous, staining pale 
purple or blue with gentian-violet (Fig. %). No trace of the 
peculiar fibrillae figured by Miss Lyon 1 in the species studied 
by her, could be seen, and it would be well if a further 
examination could be made in these species to determine 
whether or not this fibrillar appearance is due to the action of 
reagents. 
As to the nomenclature of the various spore-membranes, 
it might be better to use the term * epispore * or ‘ perinium ’ 
for the outer, sculptured membrane, considering the ‘meso- 
spore ’ as the equivalent of the exospore of the lower 
archegoniates. 
The Female Gametophyte. 
The very peculiar behaviour of the early stages in the 
development of the gametophyte was first made clear by 
Fitting. He showed that the vesicle supposed to be the 
nucleus by all previous observers was in reality the whole 
protoplast, which forms a very small, extremely delicate 
membrane containing the single small nucleus. Heinsen gave 
i 1 . c. Figs. 42-44. 
