Tiinherlahe — Swarm-Spores of Hydro diet yon. 509 



the same time, a conception tliat, however, in no Avay helps to 

 a mechanical explanation of the process. The conditions here 

 must be kept sharply distinct from those cases of tlie bipartition 

 of a single coenocytic cell by simple constriction, as for example 

 cell division in Cladopliora. In this latter case one may readily 

 imagine that the stimnhis arises in the membrane itself and is 

 either external or internal since it is a case of the construction 

 of a sino^le continuous membrane. 



When the spores are fully formed it is quite evident that 

 they are entirely separated from one another. It is not im- 

 probable that what Klebs took for connecting strands of pro- 

 toplasm was the slime wliich is sometimes found on the inside 

 of the central vacuole Ivins^ next to the vacuolar membrane. 



The general structure and form of the spores I have found 

 to be identical with tliat described by previous observers. 

 The young spores are generally almost spherical bodies with 

 the nucleus occupying a position near the plasma membrane 

 and connected with a pair of cilia which are attached to the 

 cell at the point nearest the nucleus. (Fig. 36.) In older 

 stages the portion to which the cilia are attached becomes 

 somewhat elongated and tilled with hyaline protoplasm, that 

 extends down into the cell as far as the nucleus. (Figs. 37 

 and 38.) In connection with the structure of the swarm 

 spore most interest now attaches to the locomotor apparatus. 

 This consists in all of the normal uninucleate spores of a pair 

 of cilia attached to a small spherical basal body lying gener- 

 ally in contact with, but quite clearly independent of the 

 plasma membrane. (Fig. 38.) Connecting the basal body 

 with the nucleus there are two or more protoplasmic fibres. 

 Owing to the small size of the above mentioned organs, it is 

 extremely difficult to make out any details as to their struc- 

 ture or origin. The basal body generally stains quite densely, 

 especially in the triple stain. In the best stained prepara- 

 tions it frequently appears to be of a dark red color, a fact 

 that shows quite clearlv that it is entirely distinct from the 

 plasma membrane, which, in the same preparations has a blue 

 color. In nearly all cases too it can be seen that the contour 

 of the basal body is clearly distinct from the plasma mem- 



