250 THAXTER. — MONOGRAPH OF THE LABOULBENIACE^E. 
version to a more primitive structure may be compared, perhaps, to the reversions due to wounds or 
injuries so often seen in the higher plants. Despite this very common occurrence of Peyritschiella- forms 
in probably all the species of Dichomyces, I consider the genus well distinguished by its normally sym- 
metrical receptacle and paired antheridia, this condition occurring in Peyritschiella only in exceptional 
individuals if at all. 
The most striking variation which one finds in the species of Dichomyces is connected with the pres- 
ence or aba nee of the two characteristic "auricles" which surmount the tips of the perithecia in certain 
cases. Although, the presence or absence of such peculiar structures might well be assumed to indicate 
a specific difference, it is evident that, in some cases at least, there is a dimorphism in this respect; the 
auricle. 1 form being usually smaller than the other, and even occasionally associated with it on the same 
individual, as in D. hybridus, Plate XXXI, fig. 16. More often, however, as in D. bijormis, the two are 
always separated on distinct individuals, as is shown in Plate XXXIII, fig. 1-3. This circumstance 
renders the separation of the species a matter of considerable difficulty in many cases. For example D. 
mdgatus is an auricled form occurring all over the world on various Philonthi, and is associated not infre- 
quently on the same insect with a variety having no auricles. This variety may be almost, if not absolutely, 
identical in appearance with the typical D. princeps, a species which is very common and widely distrib- 
uted on similar hosts, but which I have not found associated with individuals of an auricled type in its 
typical condition, although it is not infrequently found covering the host in great numbers. The ex- 
istence of this dimorphism, however, may render necessary the union of these and possibly other forms, 
although at the present moment I am inclined to consider them distinct. 
The antheridium in this genus, from its position and the usually dark color of the adjacent cells, is 
no easily examined; but its structure is evidently like that of most compound antheridia; the antheridial 
cells being seemingly proliferations from a subterminal cell into a terminal cell, which serves as a receptacle 
for the antherozoids as they are formed, and as a common medium of discharge. These conditions are 
indicated m a general way in fig. 4, Plate XXXII, but no form has been examined in which more than 
a very general idea of the cell-arrangement could be obtained. 
The species of the genus are confined to hosts belonging to the Staphylini.hr, and are especially com- 
mon on members of the large genus Phihmthus, some of them being more or less general parasites on 
*Z*Zt Wh,le .f erS ] a PP- r t0 b e somewhat definitely restricted in the matter of hosts. That 
numerous spec.es exist in addition to those below enumerated cannot be doubted. 
*enn hi rCga f\ !"*?*' ^ ^ ened t0 ' to revert to a Peyritsrhirlla-Mke condition, the 
: Z\. in L 7 / " * i ar f r than almost an ^ oib * r > the ^ ™***<* °f »«p«*» being 
I^EJm^* ns 5 \r through *r r Juction oi a ** «?**? 
develooed for,,, „, „!, .1 ■ ° uld •* m «""oned, however, that in some ahnormally 
'-sional.y i„ Peil L nZ A 1 h , ° ' mVCT ti0K ' P,ttle XXXI > «* 9 ' » C0I "' i,i " n "" 
members of this . 1 „ V ** See " '* an lamination of the accompanying Plates, the 
— -al' f ; ; : ;: m ,r m , 'r' form and I,izarre °» tUM «• -*•"•■* - — • "* 
striking str„,i,„,, of n""r,, M,' f° Up - 7'"' S " al<! - Iik " "* i "" 1 •PP 1 """' «5™ wth are 
unntnx nt to their condition, of life on the surface of swiftly running hosts. 
This s ,„.,i,. s whid . m , D,CH0MVCES furciff.rus Thaster. 
common in New EnJl'-'m'""^'^ "j 8 "*? 1 " "" : ty l"' of ,he »»««. occurs on small Philimlhi, and i: 
from Tillsgatc, EngUnd, and from /> ^ZTsh™ H*? 'V^ **** """»* "" '" '***" *" 
-~~_*:__i_ -r. . '"»i / . te.ura'w bharn. from T.ao \T„. — 1~~ n/r •__« \t oh. ._j-7co m 
spectively. It w 
arp, trom I ,as Mercedes, Mexico ? Nos. 364 and 752 re- 
be 
ras also found nn P j- • i 7T r ^erceaes, Mexico ? JNos. 364 and toz re- 
lonth 
