84 



SCIENCE 



[N. S. Vol. LII. No. 1334 



process may be different in different organisms, 

 but I consider it rather improbable in view of 

 tbe fact that both para- and telosynajies have 

 been described for different groups of plants 

 and animals, and especially since certain " evi- 

 dences " involved in the argument are not 

 easily observable. 



Summing up: contrary to the general be- 

 lief, so-called end-to-end conjugation does 

 offer an opportunity for interchange between 

 chromosomes at the late thick thread stage in 

 the prophase of maturation division, but at 

 this stage only. If telosynapsis is a imiversal 

 phenomenon, it would seem that crossing over 

 must take place at the stage here specified. 

 Of course, no morphological evidence has yet 

 been produced for crossing over, and the most 

 that can be said from the present cytological 

 data is that such an interchange is not im- 

 possible at a certain stage in the muturation 

 division. 



"Ward K'akahara 



destruction of zoospores of plant 

 disease organisms by natural 



ENEMIES 



In making some motion-picture photomi- 

 crographs of the liberation of zoospores from 

 the sporangia of Physoderma zece maydis 

 (see Tisdale, Jr. Agr. Res., Vol. 16, p. 137, 

 1919) the author observed destruction of the 

 zoospores by certain animalcules which are 

 commonly found in decaying vegetable mate- 

 rial. No reference has been found regarding 

 the importance of these natural enemies of 

 the plant diseases which are disseminated by 

 zoospores. 



The number of zoospores swallowed by one 

 rotifer (Proales sp.) is remarkable. When 

 the animalcules are abimdant there is a 

 speedy disappearance of the zoospores. One 

 infusorian (Eeronia sp.) was observed to 

 devour a perfect stream of the zoospores of 

 Physoderma, at the same time increasing in 

 size until it became gorged almost beyond 

 recognition. 



In active cultures one may see a field 

 in the microscope filled with millions of 

 Eoospores swimming about. In a few hours 



large numbers of these have been devoured 

 by the animalcules, which rapidly increase 

 in numbers. A few hours after this one then 

 gees these same protoplasm constituents swim- 

 ming about not as zoospores but as animal- 

 cules. The process of change is so rapid it 

 makes one wonder if there is always cleavage 

 of the proteins and resynthesis or whether 

 there may not be some shorter method of 

 assimilation especially in the unicellar organ- 

 isms in which the cytoplasms of the in- 

 fusorian and the zoospore ingested are in such 

 intimate contact. 



In starting from dry material collected 

 from cornstalks infested with Physoderma, 

 the animalcules appear first and are on hand 

 for each crop of zoosjKjres. 



It would be desirable to determine just how 

 important such animalcules are as natural 

 enemies of those plant diseases which are 

 disseminated by zoospores. Also we should 

 collect data to determine if the destruction 

 of the soil animalcules by excessive liming 

 may not be correlated with epidemics of these 

 diseases. 



E. B. Harvey 



tr. S. Department op Agricdltuee 



THE JOURNAL OF MORPHOLOGY 



At its annual meeting in St. Louis, the 

 American Society of Zoologists voted to ac- 

 cept the proposition made by Dr. M. J. Green- 

 man, of the Wistar Institute, that in the fu- 

 ture the society should assume control of the 

 scientific policy of the Journal of Morphology 

 and elect the editorial board, while the Wistar 

 Institute retained control of the financial man- 

 agement of the journal. 



A committee composed of M. M. Metcalf, 

 Caswell Grave and W. E. Castle was appointed 

 to initiate a scientific policy; to nominate an 

 editorial board; to consult with the advisory 

 board of the Wistar Institute and to refer its 

 recommendations for final decision to the exec- 

 utive committee of the society. 



This committee on publication and the exec- 

 utive committee and the Wistar Institute have 

 agreed to the following action which accord- 



