I20 PALMKR : NAVICILA SOCIALIS. 



occurred on the lip of a spring in Media, where A^. socialis 

 occurs, but only sparingly, and among a perfectly overwhelm- 

 ing mass of other diatoms. They were collected on two dif- 

 ferent occasions, both in the month of April. They were 

 always scarce in the gathering, but their unusual appearance 

 was such as to arrest the attention at once. They consisted 

 in each observed case of crystal -clear but dense and visil)le 

 jelly masses, containing each either two or four ovoid, amber- 

 brown, translucent, spore-like bodies, precisely the color of a 

 perfectly healthy Navinila. In one instance there were four 

 spores — if spores they were — arranged in one plane as at the 

 comers of a square. These bodies could not be proved to 

 have any relation with N. socialis. Paucity of material and 

 lack of an effective technique for producing further develop- 

 ment, combined for failure. Hut they were like nothing I 

 have seen described, and I have always felt a perfect confi- 

 dence that they belonged to some diatom, and just as con- 

 stantly I have suspected that they pertained to A^. socialis. 



It is along this indicated line that I look for an elucidation 

 of the groups of four. I desire in this matter the help of 

 those diatomists who are engaged in the study of the life- 

 histories of these organisms. Here is a chapter still to be 

 written, and it cannot fail to prove of great interest. 



