PROCEEDINGS OF SOCIETIES, 83 
taken much of interest, and was therefore agreeably surprised at 
obtaining so much value in various ways as on the present occa- 
sion, as evidenced by the fine specimens now exhibited. 
Dr. Moore showed some examples of an alga which he had 
noticed for some time forming a green scum on the surface of the 
water in a pan in one of the warm houses in the Botanic Garden. 
This production seemed to show three sufliciently well-marked 
states or conditions; one in which the individual rounded cells 
were combined into a dense, somewhat indefinitely formed cluster, 
occasionally presenting the appearance of being hollow in the 
centre; again the cells presented themselves as extremely short 
linear series of usually four or five cells (what might be called 
short filaments—four sometimes in a series, and a fifth at one 
side, as it were originating a branch or pseudo-branch); and 
again the cells presented themselves individually free, or it might 
be binate, owing to recent self-division. Occasionally certain 
cells were to be met with undergoing division in all directions of 
Space, and sometimes some of the dense masses of cells first 
mentioned presented short linear series of cells seemingly 
_ emanating from their circumference. It seemed, therefore, as if 
the following might represent the growth so far as the phases of 
it to be seen were concerned:—Single, nearly orbicular, cell; 
binary and quaternary division; repetition of this, and in various 
directions of space; more or less densely compact cluster; cir- 
cumferential growth; cells at periphery finally taking on growth 
in one direction of space only; linear series of cells detached ; 
repetition ; and, finally, a breaking up into single cells and, it 
might be, zoospores, many similar-looking cells occurring in an 
active condition in the water. This production appeared to be 
an annual—appearing each season, actively vegetating, and quite 
disappearing in no very long space of time. Dr. Moore stated 
he would keep a look-out as to this growth in the vessel in which 
it occurred, and inform the Club about it on another occasion. 
Dr. John Barker exhibited alive the larval form of an un- 
recognised dipterous insect, remarkable for the “home” it had 
constructed “ without hands.”” He had found it in the canal near 
Dublin. This habitation formed a case of about ;4th of an inch 
long, ={;th of an inch wide, and 1,th of an inch deep, and con- 
sisted of two elliptic pellucid valves (like a bivalve shell, only 
joined at opposite margins), and haying coiled thereon a quantity 
of the filament of Zygnema, seemingly still in active growth; 
these valves were joined together at the broad margins, and were 
not closed at the narrower margins (or the ends). Through one 
of the openings thus left, the head and anterior portion of the 
larva mostly protruded. It did not seem able to leave the case, 
but it could turn round in it or retract itself altogether within its 
bivalye covering. It was curious to observe the almost concentric 
or sometimes spiral arrangement in which the creature had 
