182 SYDNEY J. HICKSON AND J. T. ^YADS\YOKTH. 
Fig. 21. — Young Dendrosoma observed alive from free-swimming 
gemmula stage (September, 1908) and then fixed. It is 85 /j x 70 /i in 
size, the arms about 20 /j. in length, and the four micronuclei each aljout 
4 n in diameter. 
Figs. 22-29. — Series of stages seen in the mitotic division of the 
micronuclei. X 1000. 
Fig. 22.— A full-sized micronucleus in a resting condition. 
Fig. 23. — Enlarged mici’onucleus previous to mitosis. 
Fig. 24. — Micronucleus in stage of spindle-formation. 
Fig. 25 . — Stage of division in which there is an equatorial baud 
free from chromatin. 
Fig. 20. — A stage in mitosis occasionally seen in which the 
2 )oles are j^ointed and free fi-oni chromatin. The relation 
of this stage to tlie other stage in mitosis is not clear 
(see jj. 159). 
Figs. 27-29.— The chromatin is, in these stages, collected into 
the two 2 >oles wdiich are connected by an achromatic 
S2>indle. 
Fig. 30. — Dendrosoma feeding u^jon a EujDlotes (E.). The swollen end 
of the aian of the Dendrosoma (D.) was 15 fi in diameter, the length of 
the Exqjlotes body lUO /x. A stream of jxarticles (St.) could be seen 
2 >assing down into the arm through the attached suckers ; the other 
suckers were (piite indifferent. 
Fig. 31. — Side view of a gemmula of Lernajoixhrya (!■') showiug two 
of the three contractile vacuoles. None of these gemmuhe exhilxited a 
micronucleus. 
Fig. 32. — A very young, ^u'obably (juite recently fixed s^xecimen of 
Lerna'ojxhrya with only four suckei's, showing a com^xletely formed 
gemmula in position. There are no micronuclei to be seen. 
Figs. 33 and 34. — Two sketches of young Dendrosomas showing the 
method of arm formation in Dendrosoma. 
Figs. 35-39. — Series of studies of Urnula e^xistylidis e 2 >izoic on 
Dendrosoma showing the different forms assumed by the tentacles. In 
figs. 35-38 the S2)ecinieus have only one tentacle, in fig. 39 it has two. 
Fig. 40. — Section through an Uniula from a stained 2 U'eparation. In 
this S 2 iecimen the diameter of the laxly is 19 fx, of the meganxxcleus (M.) 
8'5 fx, and of the micronucleus (m.) 1'7 /x. 
Fig. 41. — Transvei’se section through an Urnula after the formation 
by fission of a gemmula (y). Drawn to the same scale as fig. 4(t 
Fig. 42.— A S 2 )ecimen of Urnula e 2 Jistylidis, showiug the body 
retracted below the mouth cf the test. Co 2 xied from Engelmann (5) (PI. 
30, fig. 13). 
