34 



MANNS (47) 1905; Wille (69) 1911 — : Chlorella possesses a hell- 

 or hall-shaped chloroplast and multiplies hy „freie Zellhildung''\ 

 the daughter-cells surrounding themselves within the mother-cell 

 each with its own membrane arisen quite independently from the 

 mother-cell-wall. Consequently, they are lying free within this 

 old wall and get at liberty by its bursting or early dissolviiig. 

 So they are aplanospores ; zoospores and sexual reproduction are 

 absent. A nucleus is present. A pyrenoide may be absent. The 

 product of photosynthesis is starch, oil or glycogen. 



On the contrary, the symbiotic alga answers exactly the defi- 

 nition given in literature — Gay (20) 1891; Artari (1) 1892; 

 Chodat (U) 1894; Oltmanns (47) 1905; Wille (69) 1911 — 

 for the Pleurococcaceae : The Pleurococcaceae possess a disc-shaped 

 chloroplast and nmltiply hy simple vegetative division of the ivhole 

 mother-cell {into two)] the new wall, forming a partition in the 

 mother-cell and sticking to the existing wall, divides this one 

 as well (into two). So they do not multiply by „freie Zellbil- 

 dung". Zoospores, aplanospores, and sexual reproduction are 

 absent. A nucleus is present; a pyrenoide may be absent (Pleu- 

 rococcus vulgaris). The wall is not so very thick, or thin (Pleu- 

 rococcus vuig.). A jellied envelope is present, but in the genus 

 Pleurococcus rather indistinct. The product of photosynthesis is 

 starch or oil (the latter in Pleurococcus vuig. and others). The 

 algae live in the air or in fresh-water. The diameter of Pleuro- 

 coccus vuig. is 3—7 [j.. 



Now, my descriptum of the symbiotic algae of the Spongillidae 

 I examined (pag. 24 — 27, 30 — 33) entirely corresponds with this 

 definition of a Pleurococcus (except that the nucleus has not yet 

 been sufficiently demonstrated in the symbiotic algae). I therefore 

 consider these algae to be a form closely related — if not identical — 

 to Pleurococcus vulgaris Naegeli. It is only in dimension that both 

 algae differ, the symbiotic one being 1.7 — 3.8 ^a, Pleurococcus 

 vuig. (according to Artari) ') 3 — 7 [/.. One might call the first 

 Pleurococcus parasiticus. 



1) Artahi calls it Pleurococc. vuig. Menegh. 



