DUBLIN NATURAL HISTOET SOCrETT. 31 



" Die Infusionsthierchen," Plate ii. Fig, 15, where a number of green 

 zoospore-like bodies are figured within and external to an empty Clos- 

 terium ; these bodies, named by him £odo viridis, and classed amongst the 

 Infusorial ("poly gastric") animalcules. I^ear the centre of the figure, 

 within the nearly empty frond of the Closterium, there is a green irre- 

 gular rugged mass. Could this be a portion of the granular endochrome 

 untransformed into "zoospores" — his animals of the species '^ Bodo 

 viridis" ? 



Having thus endeavoured to convey what I believe is the state of the - 

 question as to the occurrence of zoospores in the family Desmidiacese, I 

 will next draw attention to the accompanying figures (Plate I., Pigs. 1, 4). 

 Docidium Elirenbergii here afibrds us an example of the production of a 

 few comparatively large ciliated bodies formed at the expense of the 

 cell- contents of the parent cell, and which make their exit therefrom 

 through one or more specially formed lateral tubes. These bodies, 

 although I am quite ignorant of their after development, I cannot but 

 believe to be zoospores ; and I imagine I am justified in the conclusion, 

 their appearance and mode of formation seems to be so comparable to 

 the zoospores in Cladophora, where they undoubtedly, as is well known 

 in this as in various other algse, propagate the plant and form young co- 

 lonies in abundance. The first indication of the conmiencement of the 

 phenomenon is the production of a single minute hyaline lateral tubercle, 

 or sometimes of two, or more rarely still of three such tubercles, just un- 

 der the inflation at the base of, I imagine, the younger segment (Pig. 1). 

 This tubercle arises — and the same holds when there are two or three — 

 not from any part of the original segments, but from a special extension 

 of the boundary wall interposed between the inflated base of the seg- 

 ment and the sutural line. In other words, the tubercle is not produced 

 between the segments by their separation at the suture, but from an ex- 

 tension or addition at the base to one only of the segments. On looking 

 at the drawings superficially, it might appear that the new growth, with 

 the projecting lateral extension, was a modification of the phenomenon, 

 some cases of which were figured and described by me in our Proceed- 

 ings of last session i^vide Plate I., Pigs. 10 to 15),'^' here merely difierently 

 carried out with a definite end to meet a special exigency. But the case 

 is difierent here, for in the abnormal growths alluded to [1. c), the new 

 irregular portions were added between the old segments by their separa- 

 tion at the suture, making a third development specially belonging to 

 neither old segment ; whereas here, as I have just indicated, the new ad- 

 dition is an extension to the base of one only of the original seg- 

 ments. The growth of the additional lateral tube in the present in- 

 stance is comparable rather to the somewhat similar extension from the 

 shorter or younger cone, preparatory to conjugation, in Closterium JSkren- 

 hergii, described a little back, except that here it is usually longer (or 



* Nat. Hist. Review, vol. vi., p. 469, Plate XXXIII., Figs. 10-15. 



