DUBLIN NATURAL HISTOKT SOCIETY. 35 



the several distinct parasites seem to be nourished at the expense of the 

 contents of the infested cell, presently protruding their tubular necks 

 through its boundary wall, outside which they burst at their apices 

 and discharge exceedingly minute " zoospores," formed from what has 

 now become their own proper cell-contents, which are not green j 

 whereas, as above indicated in the phenomenon in Docidium, now here 

 for the first time described, the tubular extensions are produced directly 

 from an addition to the original cell- wall itself, and with which they 

 are in absolute continuation, and through the apices of which the cell- 

 contents of the frond are emitted by its own direct conversion into 

 zoospores, and which are green and comparatively large, after the man- 

 ner of Cladophora. Pringsheim seems to see little difficulty in suppos- 

 ing it as easy for the zoospores in Pythium, having arrived at the 

 surface of a suitable confervoid, to penetrate or absorb their way into 

 the ceU, as it is for their tubular necks in a similar manner eventually 

 to protrude from within through the outer wall. 



I have, however, lately met with a parasitic growth attacking Clos- 

 terium lunula, and which I refer doubtfuUy to Pythium (Pringsheim), 

 and of which Fig. 5 is a drawing. Pringsheim's plant, met with by 

 him in the conjugated joints of a Spirogyra, he refers to the family Sa- 

 prolegnieae. That observer suggests that a ramification of this parasite 

 may exist in the interior, so that the numerous projecting utricles may 

 possibly be connected amongst themselves within the remains of the cell- 

 contents of the infested Spirogyra. Therefore, he says that the bodies 

 with elongated necks may actually be the sporangia separated from the 

 vegetative part of the plant by a septum placed deeply beneath the con- 

 tents of the infested Spirogyra-spore. This, however possible it may be 

 in Pringsheim's plant, does not seem to hold in the curious growth 

 figured (Fig. 5). Here, at least, each individual plant seems to be a 

 flask-shaped body, without any connexion with its neighbours : in one 

 case, indeed, I noticed two of the necks to inoscidate within the frond 

 of the Closterium. In a word, each flask-shaped body, so far as I can 

 see, may be said here to combine in itself both the vegetative, as well 

 as the fructifying portion ; the whole plant at maturity being, as it were, 

 converted into a sporangium. 



In the earliest condition in which I saw this plant, the bodies within 

 the Closterium appeared rounded vesicles, each with a short neck. The 

 neck of each, by gradual extension, reaches the old cell-waU of the 

 Closterium ; penetrating which, it grows to a very considerable extent 

 into the surrounding water. Just within the boundary wall of the 

 Closterium, each shows a very decided enlargement of the neck, and 

 the extremity of each is distinctly clavate. So far it appears to agree 

 with Pringsheim's Pythium. But it diff'ers therefrom, inasmuch as the 

 cell-contents are green, not colourless, as well as in the great length of 

 the necks. 



Now I regret I am unable to affirm that the numerous orbicular, 

 spore-like bodies in the neighbourhood (Fig. 5) are the produce of the 

 contents of the organism in question, as I did not sec their production — 



