238 



membrane. Later the partition wall becomes arched from the sporan- 

 gium contents, and shortly, two membranes are formed, the one belong- 

 ing to the sporangial portion of the thread, the other to the basal part. 



The view of Rothert, confirmed by Berthold, Hartog, and others is, 

 that at the arrest of the apical growth of the hypha, the protoplasm con- 

 tinues to flow in from the base, usually producing an ovoid enlargement. 

 For a time the thick protoplasm of the sporangial part of the hypha 

 passes gradually into the basal part, but the contrast soon becomes abrupt 

 and well-defined. Then the granules disappear from the protoplasm, so 

 as to form a somewhat elongated, transparent plasma ring, which in- 

 creases at its inner circumference until it forms a transverse disk, that ex- 

 tends across the hypha from wall to wall. It is sharply marked on the 

 basal side, but on the sporangial side passes gradually into the granular 

 protoplasm. Within a very short time (about one-half minute), the 

 transverse septum appears at the base of the disk. This septum is at first 

 pale but soon becomes strongly defined. 



Rothert thinks it probable, that the material for the formation of the 

 septum is derived from the Pringsheim's cellulin corpuscles, consisting of 

 a very soluble form of cellulose, that accumulate about the limiting area. 



For the purpose of verifying one or the other of these theories, I made 

 many serial cultures of Saprolegnia ferax on the bodies of dead flies, wasps, 

 spiders, and crickets. By this means I was enabled to watch the develop- 

 ment of the partition-wall. The time at which this was formed, in each 

 instance observed, was in the morning. As to whether any especial sig- 

 nificance attaches to this fact in thie case, I can not say. In all cases the 

 partition wall was formed as set forth by Rothert, and not as formerly 

 suggested by Strasburger. 



Another point first stated by Rothert was also confirmed; namely, that 

 fragments of a healthy culture of Saprolegnia may be cut off and will 

 continue to thrive in the hanging drop and are much more normal than 

 the fly-leg cultures usually used. I found that fragments thus treated 

 continued to grow and develop from day to day. 



To make a study of the nuclei, I placed flies bearing Saprolegnia ferax 

 in difl"erent stages of development, in a one per cent, solution of chromic 

 acid for two hours ; washed this material two days in distilled water ; 

 placed it in alum-cochineal twenty hours ; and after again washing for a 

 short time, brought it gradually into seventy per cent, alcohol, for pre- 

 servation. By this process the nuclei are stained very nicely, and their 



