56 THE AMERICAN NATURALIST. [VoL. XXXV. 
Hammar's layer, the ectoplasmic layer that passes from cell to cell, 
and that the absence of lime so modifies this membrane as to prevent 
it from holding the cells together. The actual moving apart of the 
cells he thinks due to their individual movements. Yet the author 
grants that some other factor remains for future research to discover, 
since when cells that have fallen apart in water free from lime come 
together again and flatten against one another in normal water, there 
is no normal membrane present. 
That one such factor is a pathological state of the ectosarc accom- 
panied by abnormal *filose activities" seems indicated by the 
author's figures. E A. 
Vitality of Eggs and Sperms.—— James F. Gemmill! records 
some interesting observations upon the life of sperm and egg. 
Sperms of the sea-urchin, Achinus sphera, put into still water, 
move only seven inches before dying, so that their power of dissemi- 
nation must depend largely upon currents of water and not upon 
their own locomotion. 
In a tube of 2.4 mm. diameter they ascended 12.6 mm. in 7 
minutes; 31.6 mm. in 20 minutes; and 44 mm. in 45 minutes. In 
tubes of different sizes these sperms ascended a shorter distance in 
the narrower tubes. 
Sperms of an annelid were found to live longer if the water con- 
tained douz//on; hence the author infers they are able to nourish 
themselves. ; 
To keep the sperm alive long the amount of sea-water added 
must not exceed nine times the bulk of sperm. When the sperm 
and water formed an opaque white liquid the sperms lived seventy- 
two hours; but when the sperm was diluted with water till only 
slightly turbid the sperms died in three to five hours. 
That the sea-water stimulates the sperm is inferred from the observa- 
tion that even immature sperms became active when put into water. 
The eggs of this sea-urchin are in best condition for fertilization 
during the first four hours after being discharged into the water, but 
there is little loss of vitality up to nine hours. In seventeen hours 
many develop abnormally, and many not at all. In twenty to twenty- 
four hours only one to two per cent develop, and no development was 
observed after twenty-eight hours. On the other hand, when the 
eggs were fertilized immediately after discharge into the water, poly- 
spermy and irregular development were apt to take place. 
1 Journ. Anat. Phys., vol. xxxiv, January, 1900. 
