THAXTER. — MONOGRAPH OF THE LABOV LHKN I A( K.I . 21VA 
Of abnormalities more or less directly due to environment and resulting from growth under con- 
tinuously unfavorable conditions, as for example exposure to violence or insuHicieni nutrition, nun* mus 
instances might be cited in which the general form and the character of the apj>endages may have been 
thus modified. The most remarkable instance, which appears to be of this nsilure, i.s seen, however, 
in the genus Diehomyves, and results in a structural variation which may be in the nature of a i version. 
In several species, especially when large numbers grow crowded OB the legs of swiftly runninn hosts, tin 
normal symmetry is lost and *'ie individual assumes a structure exactly like that of the pirns Pi ii- 
schiella, although under favorable conditions, as on the abdomen, this form never ap|>cars. Such ;i 
condition of D. inceqiialis was formerly figured and described as a new species of Peyril hielkl, /'. viyn.-- 
reus, and it seems not impossible that this phenomenon may be comparable to reversions resulting from 
injury in the higher plants. That abnormal forms due to hybridisation may exist, has already been 
suggested above, and this may account for the confused variations seen, for i unpli . in Dtrhomyres rnl- 
gatus or D. princepg. Laboulbmia mekmotheoa, also, may possibly be nothing more than a hybrid be- 
tween L. Mexicana and some of the species with black pcrithecia often a»oeiated with it. although this 
is of course a mere suggestion. 
The Geographical Distribution of the species and geners is now >ul!i« i.nilv well known in many 
instances to illustrate various points of interest in this connection, but in ric« of the limitations of the 
present paper as to space, and the fact that large additional collections of these plants are i w awaiting 
examination and study, no general summary or tabulation of distribution will be here Attempted. Infor- 
mation in regard to distribution is most complete in reference to parasites of the ( ibi.l since thi 
family of beetles is a favorite group among entomologists, and is extremely well represented in a majority 
of the exotic collections examined. Since, also, these insects include a majority of the hosts infested by 
species of Labmdbenia, it is in this genus that the most complete data as to special instam s of distribu- 
tion have been obtained. A brief reference to the subject will be found below under this genus, but it 
may be remarked in this connection that it is singular to find a specs I like /.. mriabil infesting I vari.ty 
of common genera in both American continents, yet quite unknown elsewhere; while the distribution 
of L. Pheropsopki is coextensive with that of its host in five continents. < >f the numerous q>eciea on 
Galeritee in South and Central America none extend to Africa, where Gokriim are numerous in species, 
and are attacked by a single form only, unrelated to the South American one. Again L. Phiiomtki, which 
is the common form in North and South America on members of the v. -ry huge and unive, dly distrib- 
uted genus Philonihus, is unknown from other regions, although almost unlimited material has been 
looked over; while L. cri.stata, the only species growing on members of the large ami varied genus 
P&derus, has been found from all the continents. 
The Development of Series in the I.aboull 
directions in which this development has 
be consid 
ters of interest concerning which, however, the writer finds himself unable to arrive at any satisfactory 
conclusions. On the assumption that these plants have been derived from aquatic an, tors, one would 
naturally look to the existing aquatic forms, rather than tin- terrestrial ones, for suggestion, as to prim.- 
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compou 
type 
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