ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 283 



under the name Marchesettia spongioides. He regards the sponge 

 {Iteniera fihulatd) liere as the parasite, which, from its delicate struc- 

 ture, and the absence of any cartilaginous or calcareous framework, 

 has, for the sake of protection, attached itself to a red alga with 

 stout stem. The close union of the two individuals has completely 

 altered the structure of the alga, so that it resembles another sponge 

 of the genus Chalina ; and Marchesetti thinks we may possibly have 

 here an instance of protective mimicry. 



Vegetative Changes of Form in Chlorosporese.* — G. Schaar- 

 schmidt finds that changes of form take place in many green algae, 

 which he compares with those of the Schizomycetes. The following 

 are the series, as he describes them, in the case of Conferva homhycina. 



In the normal condition (F. 1) the cells are cylindrical, 1^-2 

 times as long as broad, and with large chlorophyll-grains. When 

 fresh filaments are about to be formed, the cells imdergo their first 

 change in form, become narrow and barrel-shaped (F. 2), and divide 

 when their length has doubled. From this j)oint division proceeds 

 more actively, but the division- walls are, with few exceptions, no 

 longer parallel to one another (F. 3). Some of the cells now lose 

 their contents, and are compressed by the pressure of the adjacent 

 cells. The division now attains its maximum of energy ; some of the 

 mother-cells become segmented, by rapidly successive and very thin 

 cell-walls, into sixteen or seventeen daughter-cells (F. 4). In these 

 divisions, the walls of the mother-cells are easily recognized by their 

 H-sLaped remains, which bound on either side the row of daughter- 

 cells. A short-celled filament now results from the thickening of 

 the septa (F. 5) ; but in some exceptional cases, short-celled fila- 

 ments, 2-3 times as broad as the ordinary ones (F. 6), are found, 

 not dissimilar from those of Vlothrix. These are again segmented in 

 the ordinary way (F. 7). After the divisions have been many 

 times repeated (F. 8), 4-8 daughter-cells are developed in the 

 mother-cells of filaments of both kinds (F. 9) ; and the divisions 

 are now completed. The cells containing the daughter-cells swell 

 up irregularly, the filaments become ribbon-shaped, resembling 

 Sirosiphon, curve, and assume forms in which they might readily be 

 mistaken for the microsporiferous filaments of Ulothrix. The daughter- 

 cells divide, after their cell-wall has been developed, and become free 

 by the bursting of the mother-cell wall, like Sdiizoddamys. These 

 cells, now free and already segmented (F. 10 a), closely resemble 

 Gliroococcus turgidus, and form the transition to the Protococcus-ioim. 

 (F. 10 fc), breaking up into two cells which become free Protococci 

 (F. 10 c). The further development of these cells is still unknown ; 

 in some cases a quadripartition has been observed, leading to the 

 Oocystis-stsite. Eesting-cells were also observed, formed by the 

 thickening of the cell- wall of cells swollen into a spherical form. 

 They are not unfrequently formed, three or four adjacent to one 

 another (F. 11). 



A similar series of forms is described in the case of another 



* Magyar Nove'u. Lapok, vii. (1884) pp. 103-13 (1 pi.). See Bot. Centralbl. 

 XX. (1884) p. 354. 



