232 Barrett. — Development and Sexuality of some 
extra cellulam matricis valde prominente ornatis ; zoosporis minutioribus, 
elongatis ; ciliis duobus, apici v. proximis apici insertis ; oosporis sphaericis, 
2 5-5° n diam., endosporio crasso, episporio tenui, spinis numerosis, conicis, 
basi dilatatis, apice acutissimis ; antheridiis sphaericis, saepe ovalibus ad 
elliptica, 10-25 P diam., membrana levi hyalina inclusis. 
Hab. in Aphanomyces laevis , de Bary, Ithaca, N.Y. 
This species is made not unmindful of the fact that the form resembles 
rather closely in some respects O. minor , A. Fischer, especially as described 
and illustrated by Petersen ( 19 , p. 405). The fact that the spines are much 
more slender than those illustrated by Cornu (6, PL IV, Figs. 3 and 4) and 
that this form could not be transferred to the hosts on which O. minor , 
Fischer, was found, seems to the writer to warrant the establishment of a new 
species. 
Olpidiopsis Saprolegniae , Cornu. 
Sporangia single or multiple, formed in terminal or intercalary swellings 
of the host hyphae, elliptical, oval to spherical, very variable in size, up to 
150/x in diam., with one, less commonly two, exit tubes ; zoospores oval to 
elongated, with two cilia attached at or near the anterior end. Oospores 
spherical, with one or two, less commonly three, antheridia, with a thick 
endospore and a thin exospore bearing numerous slender spines up to 10/x 
long in large specimens ; oospores very variable in size, up to 107 \l in diam., 
provided with oil globules ; antheridia spherical to oval, with a smooth 
colourless wall. Germination of the oospores not observed. 
Parasitic in Saprolegnia species. Ithaca. 
This species is in some respects similar morphologically to O. luxurians . 
Cross-inoculation experiments with the two species and their hosts revealed 
that neither could be transferred to the host of the other. This would 
indicate that they were at least biological, if not morphological, species. 
The spines of the latter are slightly more slender than those of the former. 
The description as given above for O. Saprolegniae differs in some 
minor points from that prepared by Cornu, but on the whole seems too close 
to it to warrant the formation of a new species. 
5. General Considerations. 
The presence of true sexuality in the Chytridiaceae is, indeed, rare. 
Urophlyctis and Olpidiopsis have been supposed to possess such a stage, but 
no cytological evidence has been brought forth. Fisch ( 10 ) described the 
copulation of small motile gametes in Reessia, while Sorokin ( 22 ), according 
to Butler ( 4 ), reports a similar phenomenon for Tetrachytrium . A. Fischer 
( 13 ) accepts neither of these results, but in view of the fact that Griggs ( 14 ) 
has recently reported a similar condition as existing in his new genus 
Monochytrium , their correctness seems more probable. An interesting 
