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IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
most variable amoeboid form within my knowledge. During 
two months observation these abundant animals were a most 
interesting study and their phases filled many drawing plates. 
A nucleus could not definitely be made out, though many re- 
agents, including osmic acid, were tried. At no time was a 
contractile vacuole seen,, nor were the animals seen to divide. 
Figure 22 shows an individual which I regard as the same 
species, but which lias a gelatinous covering like Heterophrys. 
Conn, in his Protozoa of Connecticut, also records Xuclearia with 
a gelatinous envelope. 
Professor Calkins who kindly confirmed my identification of 
this species says: ‘ ‘ F rom your sketches I have no hesitation in 
saying that your organism is one of the questionable heliozoa most 
closely related to Aclinopkrys, and you are right in identifying 
it as Nuclearia delicatula Cienk. ” In Calkin’s Protozoology 
(1909) he places Xuclearia with V amp\yrella in the Proteomyxa 
on the basis of its amoeboid character and the rare anastomosis 
of pseudopodia. Edmondson does not record the genus. 
Subphylum MASTIGOPHGRA 
Class I Zoomastigophora 
Subclass FLAGrELLIDIA. 
*Olkomonas species 1. .25, figure 55. 
Minute, plastic, sometimes attached by a temporary posterior 
prolongation. Flagellum single with a fissure at the base. Body 
oval, not compressed, crenulated in optical section, with a 
minute posterior tip. Flagellum vi'bratile. Vacuole large, an- 
terior. Nucleus posterior. Found in old infusions in the lab- 
oratory. Uncommon. Length of body 19 microns, flagellum 
20 microns. 
* Oikomonas species 2. 26, figure 55. 
Similar to the preceding, but lacking crenulations and pos- 
terior tip. Flagellum longer, vacuole and nucleus not visible. 
Transparent. Abundant in gold fish tanks with Xuclearia. 
Body length 20 microns. 
*Rhipidodendron splendidum Stein. 23 and 24, figure 55. 
Monads ovate, similar to Antliophy sa, living in a social zoothe- 
cium, a rust brown ‘ Mabellate or dendriform aggregation of 
closely approximated tubules,” the distal ends of which are 
each inhabited by a single zooid. Only a large number of dead 
