154 The Significance of Sex. [Feb. 
character. In some forms we get either many small nuclei or 
else granules, besides one or more chief nuclei, and, according to 
Altmann, this is true of all tissue-cells, so that we have nuclear 
bodies first differentiated in two directions, the granules serving 
some nutritive or other function, while the nuclei retained the 
office of being the primary reproductive bodies. 
The next differentiation arising would be the differentiation of 
the nuclei into two kinds, which in some Ciliates have acquired 
considerable independence and act quite differently during di- 
vision. We know them as nuclei and nucleoli, or as nuclei and 
paranuclei, respectively. Better terms are Huxley’s endoplast 
and endoplastule, as not implying homologies which are probably 
false. In massive nuclei the chromatin exists in a fine net-work, 
which gives the appearance of granules in the resting phase and 
of fibrillz during division. In Gastrostyla the endoplastules 
divide by a true spindle and a nuclear plate of karyosomata. 
Nearly all the nuclei of Opalina are of this sort. 
The substance of the nucleus may differentiate into two sorts 
that gather in two portions of the nucleus, either by polar dif- 
ferentiation or by centripetal differentiation. One substance is 
hyaline, the other granular; examples are Leptodiscus, Spirochona, 
and Noctiluca. In Spirochona it is the endoplast which has this 
structure, and it divides by a complex kinesis. A nucleolus 
appears in the clear part, which becomes transformed into fibrils 
while the hyaline portion gathers as two polar plates that sepa- 
rate, and so, as it were, tear the nucleus in two. The three 
endoplastules present divide by simple constriction at the same 
time; and here also there are polar plates of a substance different 
from the equatorial portion. 
| Ina different direction we get the vesicular differentiation, and 
this is most common in the lower Protozoa, and is that from 
which the metazoan cell-nucleus is derived. In Rhizopods we 
may not only get many nuclei (about two hundred in Pelomyxa), 
but each nucleus may present a great variety of phenomena. 
There may be a central nucleolus, and this nucleolus may be 
composed of many microsomata, or the microsomata may sepa- 
rate as so many nucleoli, or again may fall into granules. To- 
gether with all these forms there may be a cortical shell of 
micros¢ for examples, see Figs. 14, a, b, 20, 22. The 
= -  multin clearity of many of the Protozoa is due to the fact that 
