1904] THAXTER: NOTES ON MYXOBACTERIACEAE 413 
forming irregular, often variously confluent masses. Cysts 
irregularly rounded, subspherical to ovoid, irregularly angular 
or subcylindrical, divided into an irregular number of secondary 
cysts through clearly defined pseudosepta, the septation trans- 
verse or various. Cysts 18-22 12-224. Secondary cysts 
about 10-124. Rods 3-5 x 0.8-Ip. 
On horse dung, Cambridge, Mass. : 
This curious form has appeared twice in laboratory cultures, and is at 
once distinguished by its compound cysts, the septation of which is so regu- 
lar and clearly defined that they have the appearance of fungus spores of the 
phragmosporic or dictyosporic type. The peculiarities of the species result, 
as is evident, from three successive aggregation impulses; first the general 
heaping up of the rod-mass, next the secondary aggregation of groups of 
rods within this mass to form the primary cysts, and lastly the ultimate 
aggregation of groups of individuals in these cyst masses by which they 
become divided into portions of considerable uniformity. The gelatinous 
matrix which holds the primary cysts loosely together is often scarcely dis- 
tinguishable, and hardly to be compared to the well marked envelope of 
P. vitellinum. Although this as well as the following species differ in so 
marked a manner from the type, both in this respect and from the presence 
of compound cysts, it seems undesirable to separate these forms generically, 
especially in view of the fact that P. sovediatum, described below, appears in 
a manner to connect the two conditions. 
Polyangium compositum, nov. sp. Plate XX VII, figs. 29-30. 
Color dull yellowish-orange changing to dark red on drying. 
Sori irregularly scattered or loosely grouped on the surface of 
the substratum, consisting of one to several, rarely more than 
six, irregularly rounded primary cysts surrounded by a more 
or less distinct common gelatinous envelope. The primary cysts 
irregular in size, elliptical to irregularly rounded or variously 
lobed or elongated, divided into very numerous secondary cysts 
which are irregularly polygonal from pressure, and thin-walled, 
tending to become more or less evidently arranged in definite 
secondary groups within the primary cyst wall. Larger sori 
about 100 X 170m. Primary cysts 75 X 125-35 X 35H, average 
about 75 X 100. Secondary cysts about 10-154 in diameter. 
On rabbit dung from Sandy Run, S. C. 
This peculiar form appeared on a somewhat old laboratory culture while 
the present paper was in preparation. It is very inconspicuous from its small 
