122 W. ARCHER. 



midian of exceptional structure, of which more, it is to be 

 hoped, on a future occasion), under the (provisional) name 

 of D. constrictum. This summer, however, T found this 

 rhizopod (in Connemara) for the first time nestling in the 

 mucous investment of the little alga of similar habit, Cosmo- 

 cladium Saxonicum, de Bary. The test is smaller than that 

 of Microg. socialis, less pear-shaped, does not appear to offer 

 at least any marked bilateral symmetry, is much more slow 

 in movement and in flow of the granules in the plasma of 

 the pseudopodia. In fact, one has to watch it a long time 

 to notice any alteration, which, however, can be seen by 

 close attention ; still I had seen it several times before I 

 thought it was a thing of life at all, so inert is it. I never 

 saw any " Cystophrys " condition, nor even so large groups 

 as even the minor ones oi Microg. socialis, two only, or at most 

 three, in mutual connection by the pseudopodia. The whitish 

 nucleolated nucleus and very obscure vacuoles are there, as 

 in the other form, whilst occasionally one can see subdivided 

 individuals. Though having so little to communicate on 

 this form beyond the record of its existence, and offering 

 the accompanying effort to convey an idea of its aspect, 

 leaving out of view any attempt to show the thick, some- 

 times semiopaque and striated,^ mucus in which it nidulates, 

 I feel quite inclined to believe it will turn out to be in reality 

 specifically distinct. 



Plagiophrys sacciformis, Hertwig et Lesser^ (PI. VIIT, 



fig. 11). 



considerably resembles in figure PI. cylindrica. Clap, et 

 Lachm. Like that species it is irregularly cylindrical, atten- 

 uated towards the end, the membranous test irregularly 

 wrinkled and capable of certain slight alterations of figure. 

 As in other forms the body-mass completely fills the test, and 



' This striated appearance of the mucus is due to certain radially but 

 irregularly arranged, if I might so say, tubular passages therein, in which 

 lie little more or less elongate Bacilli, or at least short bacillar filaments of 

 " Oscillatoriaceous" nature, when detached by pressure or otherwise, en- 

 dowed with a spontaneous backwards and forwards tottering kind of 

 movement, as mentioned by me in the ' Dublin Microsc. Club Minutes.' 

 Many Desmids and other Algaj besides the two above mentioned are prone 

 to harbour these Bacterian (?) organisms which can sometimes be seen 

 moving up and down inside the tubular passage through the mucus, to 

 and from the body of the alga, and, as has been said, may sometimes ulti- 

 mately make their way off altogether from beyond the periphery of the 

 mucous envelope. I am not aware whether or not this curious phenomenon 

 has been noticed by other observers. 



» Loc. cit., p. 114, t. Ill, f. 3. 



