1921] | CURRENT LITERATURE 469 
therefore of fundamental importance in fish culture. Although little is known 
yet as to which plant species are best for oxygenation, it is probable that 
evergreen species with finely divided leaves are the most satisfactory. It has 
long been known, of course, that plants are the basis of all fish food, but we 
are only just beginning to determine which species have the greater food values. 
Another thing of importance is the determination of the optimum association 
of species in a pond.—H. C. Cowtes. 
Cytology of Synchytrium and Urophlyctis.—Within a year considerable 
light has been shed on the puzzling problems of cytomorphology in the Chytri- 
diales by reinvestigations of Synchytrium (Chrysophlyctis) endobioticum and 
Urophlyctis alfalfae. The careful and thorough studies of Miss Curtis? on 
Synchytrium and of Jones and Drecuster® on Urophlyctis deserve particular 
notice. The most noteworthy results of Miss Curtis’ study of Synchytrium 
are the establishment of the occurrence of gametic fusions in the life cycle 
and the demonstration that a prosorus is regularly antecedent to the develop- 
ment of the sporangial sorus, the contents of this body passing into the host 
cell where segmentation into sporangia and production of zoospores take 
place. During the development of the prosorus from the infecting zoospore 
a series of nucleolar discharges of chromatin occurs, and the five chromosomes 
originate also from the nucleolus; but all divisions from the primary nucleus 
to the zoospore primordia are typically mitotic. The asexual or sexual nature 
of the motile cells terminating this series appears to depend on the availability 
or lack of water during maturation; if water becomes tardily available simul- 
taneous germination of a number of sporangia occurs and their zoospores 
pair, probably exogamously. Unpaired zoospores and zygotes penetrate 
growing parts of potato plants; the former reproduce the prosorus 
but the zygotes develop into resting sporangia. In the production of the 
latter no form of mitotic division was observed. Chromatic granules appear 
in the cytoplasm following nucleolar discharges, and after a further loss of 
chromatin (a process homologized with reduction) the granules become 
zoospore primordia. The existence of sexual fusions between facultative 
gametes is hypothecated for all Synchytriaceae which produce true resting 
spores. The validity of Chrysophlyctis is rejected, and the writer prefers the 
broader generic name eis to Pycnochytrium, to which the organism 
in all respects conform 
The absence of altel in the development of the resting sporangium and 
the conception of nucleolar gemmation taking the place of meiotic divisions 
The life history and cytology of Synchytrium endobioticum 
7Curtis, K. M., The ase in potato. Phil. Trans. Roy. Soc. London. 
and DrecHsLteR, CHarLEs, Crown wart of alfalfa caused by 
idm alfelfae. Jour. Agric. Res, 20: 205-324. pls. 47-56. 1920 
