ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
3G9 
of the plasmodes of Myxomycetes themselves aro taken up, coalescence 
takes place between the two plasmodes if they are homogenous, but not 
if they are heterogenous. 
With regard to the nature of the enzyme which causes the digestion, 
it appears to belong to the class of trypsins rather than to that of 
pepsins, since the digestion proceeds not only when the reaction is acid 
or neutral, but also when it' is alkaline. 
Protophyta. 
a. Schizophyceee. 
Development and Classification of Protococcoidese.* — Herr A. 
Artari has studied the structure and history of development of a number 
of Protococcoideae, especially the following : — Chlorococcum infusionum , 
Gloeocystis Nsegeliana sp. n., Pleurococcus vulgaris, P. simplex sp. n., 
P. miniatus, P. conglomeratus sp. n., P. rcgularis sp. n., P. Beyerinchii 
( Chlorella vulgaris), Dactylococcus infusionum , Porphyridium cruentum, 
Raphidium Braunii , Clilorosphsera angulosa, C. Alismatis, C. endophyta, 
G. consociata, Chlamydomonas apiocystiformis sp. n. The general result 
of his observations is that the species examined are independent organ- 
isms, not stages in the development of higher forms ; and that, where 
this has been stated to be the case by other authorities, it has been the 
result of their having had under observation organisms which are not 
true Protococcoideae. The effect of changes in the external conditions on 
the various organisms was carefully studied. 
Chlorococcum infusionum was found to propagate itself exclusively by 
zoospores or motionless gonids, never by cell-division. Pleurococcus is 
distinguished from Chlorococcum by not producing zoospores ; it is pro- 
pagated entirely by cell-division. Several species of this genus exhibit 
in some points an affinity with the Hydrodictyeaceae, especially with 
Ccelastrum and Sorastrum. Dactylococcus was never observed to produce 
zoospores. Clilorosphsera angulosa has both modes of propagation. 
The author divides the Protococcoideae into eight families, viz. 
Glceocystiace/E fam. n. ( Gloeocystis , Palmella, Schizochlamys, Palmo- 
dictyon, Palmophyllum, Dimorphococcus), characterized by the cells being 
imbedded in gelatin or attached to gelatinous stalks, Pleurococcaceae 
( Pleurococcus , Eremosphsera, Nephrocytium, Oocystis , Raphidium, Scene- 
desmus, Dactylococcus, Selenosphserium, Crucigenia , Actinastrum , Porphy- 
ridium), Chlorosphaeraceae, Tetrasporaceae, Chlamydomonadaceae (includ- 
ing Phacoteae), Volvocaceae, Endosphaeraceae, and Hydrodictyaceae. 
Sporangial Form of Diatoms.| — M. P. Miquel has succeeded, in 
diatom-cultures, in obtaining the maximum or auxosporal form, often 
called sporangial, in several species belonging to the Melosirese and 
Nitzschieae, viz. Melosira nummuloides, M. varians , Cyclotella comta, 
Nitzschia palea ; the last species is especially favourable for the observa- 
tion of this phenomenon. When the cell has attained its minimum size 
by repeated bipartition, its protoplasm swells up, separates the frustules, 
and escapes to the outside, surrounded by’ a membrane of cellulose, 
the existence of which can be demonstrated from the first by reagents. 
* Bull. Soc. Imp. Nat. Moscou, 1892, pp. 222-62 (3 pis.), 
t Comptes Rendus, cxv. (1892) pp. 615-7. 
2 C 
1893. 
