ARCHER 01* ASTERIDIA IN PENIUM DIGITUS. 145 



In a gathering which I had made in the previous year — not, how- 

 ever, from the same locality — I took a quantity of the common desmi- 

 dian, Penium digitus (Breb.), and a considerable number of them showed, 

 some individuals one, the majority two, and a few three, quite identical 

 stellate bodies in the interior of each cell ; these seemed to me evidently 

 to have been formed at the expense of the individual Penium in which 

 they occurred. Some of the Penia showed their cell-contents partially 

 absorbed, and the remainder dead and brown ; whilst others did not 

 exhibit a trace of the original contents, but contained the (generally) 

 two spinous bodies, green and vigorous, one in each half of the old cell- 

 cavity of the Penium, the outer wall of which still enveloped them, 

 but afterwards these bodies might be found abundantly without the en- 

 compassing old membrane of the Penium, and usually distributed in 

 pairs over the field (PL VIII., Pig. 4). 



Now, although in the second instance (the first here mentioned) in 

 which I had found these curious-looking spinous or stellate bodies I was 

 unable to trace them back to a Penium, their identity in appearance in 

 every way, and the fact of their having been found distributed in pairs 

 (as if left behind by the dissolved or decayed outer membrane of a Pe- 

 nium), seems most strongly to indicate that both were one and the same 

 thing, and, in fact, that in both instances these spinous bodies owed 

 their origin to Penium digitus. 



These bodies are, in fact, the " Asteridia" of the Penium, to adopt 

 Shadbolt's and Thwaites' term as applied to the still enigmatical stellate 

 or spinous bodies occurring within the cells of other Conjugatse,* and, 

 like such similar bodies, these, too, must be regarded, 1 apprehend, as 

 parasitic growths. These are, indeed, altogether unlike the smooth, 

 rounded, or irregularly- shaped, opaque, brownish, spore-like bodies 

 often seen in various species of Desmidise, whose nature continues 

 equally problematical. The latter, indeed, may be possibly related to 

 Chytridium (Al. Br.), or to Pythium (Pringsh.). 



In the same gathering I presently noticed likewise a number of 

 slightly smaller green and smooth cells, in some of which a directly trans- 

 verse well-marked light line could be seen, indicating a commencing 

 self-division. A few such bodies were seen loosely invested by a colour- 

 less coat, which coat was externally covered by slender spines ; these 

 loose external coats stood off somewhat from the inner spherical, 

 smoothly rounded bodies ; the latter afterwards made an exit by a large 

 rent in the spinous outer coat. 



Now, Pringsheim records a similar condition in certain " Asteridia" 



* Similar bodies also occur in the cells of other plants — as, for instance, in Nitella — 

 as recorded by Reinsch (" Morphologische, anatomische und physiologischeFragmente," 

 p. 8, t. ii., f. 11). Shadbolt first mentioned them in a Ulothrix, and de Bary has observed 

 similar in Vaucheria (op. cit., p. 62). Pringsheim, de Bary, and Reinsch seem to lean 

 to the view that they are of parasitic nature. 



