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THE BioLtocy oF EPHYDRA SUBOPACA LOEW 585 
back. This movement is carried on with great frequency, about two 
hundred times a minute. The current, which carries food materials into 
the alimentary canal, can be seen through the semi-transparent skin. 
A number of air bubbles move along in the convoluted tract. The larva 
also crawls in the dirt at the bottom, picking up food materials from the 
bottom surface and selecting them from within the mud. 
Selection of food— The food of the larva consists, in the main, of micro- 
scopic organisms living in the salt water. The green and yellow tinge 
in the pools, and the brown scums in the overflowed areas, are the chief 
natural sources from which the larva selects its food. Aldrich thinks 
that an alga of the Nostoc group, which is common everywhere in Great 
Salt Lake, often forming rotting deposits, must be the food of the Ephydra 
group. In the pools where these observations were made, no Nostocs 
have ever been found, but algae of other groups, green and brown, are 
found in considerable quantity. In the old pools, in which there is now 
very littlesalt, massesof Ulothrix float in thewater. These plants probably 
furnish both shelter and food for the larvae. Evidently the larvae do 
not live on one particular kind of plant material. Besides algae, some 
decayed leaves, fragments of decayed grass stems, boards or logs, even 
some microscopic animals, such as Protozoaand bacteria, may be consumed 
by the larvae. Besides organic food, some inorganic substances, although 
undesirable, may get in the alimentary canal, without being digested. In 
studying the food selected by the larvae, twenty alimentary canals have 
been dissected and examined in the field under the microscope, and also in 
the laboratory immediately after the specimens were brought in. The 
materials constituting the stomach contents, that are recognizable and 
identifiable, are listed as follows: 
. Specimens 
Lei lotelees (oer canlecstn hee (jk Ol elitet 25 eS (eas (ploy Gy elias 19 | 20 
Winders eases: BF ee cn |e | ste eee Me iscaliitsil| cw eee eenel caller eck pict eealinculirc 
IRON TURNS Son onoS OOO eee Sess SOAS SSS, lo Seliso SOS WN Sales dlr] ll Giilss all “@ Ike se 
BEOQHSAR op opoce ob SOC Ris easel | etal PENS liane leceaes Pets cael [eee VAR ea tae Faves cel tema fda [Chen mk TH ed [en 
and orinapemeer serch. c Pa | Caer Ve es een | re Ue at | ES EA 7a lt eee et cies Lear etceal pee Fe meee Bs 
Worticellaie) 2.25. f. val WA FATT Lee COME |g | cxaases | se lcs cl | covet [reat Mere stl Pane eea Ie erseeal PRPs I ele [stesaea| Piste ca] eaters /aest] le ewed] VRE 
Mastigophora.......... 3a esl PE SES EA ll pesca least [Ceres lected] Megha | sce Foam Helene [aes ALi eien| titel Mee aed Ue moar Meaney | 
(GlGeocystisee ec... ss ss ek Fel oneal | Beata | esevta| list i co a [evel etawice|soeesae | aid eseeaael Nearer eset tren teeta lie led hes eres | mets feet fags 
PASCASIO MoS stay cial toelese:'s: cess 35 fo] Nebeal (ates ketrotey | cvoxs! [by aed le en ue A Tested Peon | earl coer Late ern Ve ln tt a a le 
UNTER 6 oro Cop Bese Il o8 Ulin alls'o-olfoeo||4o,o]5 ell Halal Seal [aaollssollotollecollaodlos bon «llc ollian| (doollee 
SARC Ab oo ee Ronee 5 hed |58| LBB) | Gamal boro (feet al eectee [tat ucnl eve el sree |les Geel eee pesrecl Pe fetes || Merck | Saal [secured ft A facts) 
Chlamydomonae....... OO C-Cib © fh CO [POs cleGelse SOs ollon |) CUNO ee Geena BG alloc 
INE AGUIE). es 4 COREE ve| ¢c | c¢c|]e¢]e¢!]e¢}]e]etlvelve|ve| ec |] cc] c!]et}et)lvel vel vel ve 
| 
c, Common; ve, very common, s, scarce 
