Protoplasm in Coenocytic Hyphae. 501 
in the same direction as on the previous day was seen, with 
occasional interruptions, and one backward movement for 
a distance of about twice the diameter of the filament. At 
3.30 p.m. the observations were renewed, and for half an 
hour streaming in the same distal direction with occasional 
periods of quiescence was noted. At 4 o’clock a reverse 
movement of full strength continued for several minutes, 
then changed to the former distal course. In this way the 
reverse or proximal movement alternated several times with 
the distal movement during the next half hour. The observa- 
tions were now abruptly terminated by an unfortunate dis- 
placement of the microscope. 
It is possible that the drops upon the hyphae, which appear 
to precede streaming, are formed by the action of some 
excreted osmotic substance, as suggested by Wilson 1 in 
case of Pilobolus crystallinus ; but it seems to me more 
probable that the position of the drops is determined by 
the localization of a cytohydrolytic ferment, which acting 
upon the wall renders it more permeable, and the internal 
pressure then forces out the water. This hypothesis would 
also explain the extension of this particular watery part of 
the cell-wall into a branch. A similar suggestion has been 
made by Marshall Ward 2 in connexion with the study of 
a species of Botrytis , in which the extrusion of enzym-drops 
was observed. But the drops upon the Mucoraceae are 
undoubtedly of a different nature from those seen by Marshall 
Ward, for in Botrytis they appear usually at the tips of the 
hyphae 3 and remain there as growth continues ; in the Muco- 
raceae they are lateral, and the branches grow through and 
beyond them. An enzym has already been separated, in fact, 
from Rhizopus nigricans by Kean 4 , which is capable of soften- 
ing cellulose walls, and probably is produced by other members 
of the Mucoraceae ; but in what part of the fungus it resides 
has not been determined. 
1 Unters. a. d. bot. Inst, zu Tubingen, i, 15. 1881. 
2 Ann. Bot. ii, 331. 1888. 3 1. c. 339. 
* Bot. Gaz. xv, 173. 1890. 
