1894.] MICROSCOPICAL JOURNAL. 203 



from the larger groups on opposite sides of the frustule, 

 there being a rather wide clear space in which the spher- 

 ules did not congregate but merely crossed and recrossed 

 in their movements. 



In Prof. Smith's figures of Surirella, these spherules 

 are indicated rather sparsely, but in the first two spec- 

 imens observed by myself they were quite numerous and 

 of a uniform size. Outside of the actively motile spher- 

 ules, there was nothing else of special interest to hold 

 the attention, as the endochrome was apparently struct- 

 ureless, but showing different phases of opacity and den- 

 sity. Faint flecks or cloudlets of endochrome could be 

 seen along the central portion of the frustules, a little 

 more densely aggregated at its middle portion where the 

 nucleus or nuclei are thought to exist, and which, as a 

 partition confines the spherules, and apparently deters 

 them from passing freely from one end of the frustule to 

 the other end. 



It happens with Surirella, as with most of the larger 

 Navicuhe, that while they are being observed on the su- 

 tural face, they turn over, presenting the valvular or 

 lined faces to the observer, when it is not then so easy 

 to study the aspects of the motile spherules above re- 

 ferred to. Motile spherules of a similar character or 

 behavior, were never seen by me in any previous study 

 of any of the larger Naviculse, and as Prof. Smith's 

 specimens of Surirella, and those watched by myself, 

 agree in all essential particulars, we may regard the 

 spherules as a persistent character of the Surirella, 

 although a period of at least twenty-five years has passed 

 between the observations made by Prof. Smith and my 

 own. 



Prof. Smith, in following throughout the full process 

 of conjugation of two individuals of Surirella elegans, 

 followed the motile spherules, from the beginning of the 

 point of fusion of the two separate endochromes and en- 



