6o L1NNJ3AX SOCIETV OF J-O.V])ON. 



The coiitlitiou of stagiuitioii appears to mo to be coiulucive to 

 coiiiui;ati()ii. Filaments of ^piro'Hira frequently become coated 

 with debris of various iiiiids during tlie process, and tlie "bacteria' 

 associated with the Glyn material constitute a notable feature. In 

 addition to JJesmids, enormous num[)ers of IScenedesmus ohliquus, 

 cells of a species of T(>/'m^<, filaments of tSj)iroc/i/ra with zygospores, 

 and CEdot/oiiium with ougonia. and many larvae were present. 



It is well known that Desmids have the power of locomotion, 

 and that their movemt-nts are influenced by light. They usually 

 set themselves so that the longer axis points in the direction of 

 the sLrongest illumination, and they occasionally swing round on 

 one extremity. These Desmids are almost as broad as they are 

 long, nevertheless the movements probably occur, and the debris 

 witii whicii tliey are associated acts bolh as a helpiuid a hindrance 

 in this : it forms a substratum for their sup|>ortand prevents them 

 from becoming widely separated, so that they become associated 

 in large numoers. It is rather noteworthy that the greater 

 number of Desmids composing this association are almost of the 

 same size, namely 26 yn to 30 /x ; they almost look as if they had been 

 sifted, though there are at least three s|)ecies present. They may 

 be found in several positions, and their movements seem to be 

 due to gamotactic rather than lieliotactic force. 'J'lie Desmids are 

 arranged symmetrically and asymmetrically, both in front and in 

 apical view as well as superposed. 



The three-r.iyed form of Desmid is more abundant than four- 

 rayed, and, as might be expected, the conjugation of the two 

 three-rayed forms is the most common ; I have several times 

 seen the conjugation of a three-rayed with a four-rayed form, but 

 have not yet observed the conjugation of two four-rayed modili- 

 cations, though I have searched for this. It will be noticed that 

 when the zvgospores germinate, three-rayed Desmids sometimes 

 occur in the same protoplasm with the four- rayed forms — that is 

 to say, that the same spore gives rise to both kinds simultaneously. 

 Desmids with a four-rayed end and a three-rayed end are also met 

 with. 



In the early stages of the conjugation of tlie Desmids there is 

 a protrusion of protoplasm from the plants. In a specimen which 

 I iiad under observation for an hour or so immediately after its 

 removal fron) tlie river pool, the granules in the protoplasm were 

 "dancing" conspicuously in this protrusion, and they continued 

 in movement until I was obliged to leave the microscope. The 

 material had dried up when I again examined it. As a rule there 

 is no conjugation tube, and the contents of the two Desmids com- 

 mingle in the water. I was fortunate enough to secure one 

 specimen, however, in whicli the somewhat uncommon formation 

 of the conjugation tube was well shown. The total length of the 

 two Desmids and the tube was about 70^. The Desmids were 

 about 28 /J in length and almost of the same diameter. The con- 

 jugation tube was about 30 fj. in length, perhaps 35 fj in extreme 

 measurement, there was some overlapping, and it varied in dia- 

 meter from 10 fx to 15/u. The Desmids were asymmetrically 



