644 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
thick. These sections so fully revealed the true structure of the ectosare 
that nothing further was needed to show how completely this agrees with 
the view that the nettle-threads are nothing but greatly stretched cilia, 
that are probably extended by some physical action exerted upon them 
by the tannic acid that has both stretched and swollen them. The 
ectosare of Parameecium is composed entirely of a system of vertical 
rods of a plasmatic substance that stains somewhat more deeply than 
the endosarc. These rods compose more than four-fifths of the substance 
of the ectosare and they are so closely packed together that their arrange- 
ment can very readily be made out to correspond to the origins of the 
cilia from the cuticle. The sections showed that, where the cuticle was 
intact, and where reagents like osmic acid or corrosive sublimate have 
provoked the discharge of the nettle- threads, there are no cilia ; where, 
on the other hand, there has been no discharge of nettle-threads there 
are cilia present. No one has yet said that he has seen the threads 
discharged except under abnormal conditions. Mr. Ryder has watched 
the organisms feeding by the hour, but never once saw the slightest 
tendency to throw off nettle-threads except when crushed, roughly 
handled, or brought under the influence of reagents. 
Structure and Division of Nucleus in Spirochona.* — Prof. E. G. 
Balbiani has studied Spirochona gemmipara , and has reached the follow- 
ing conclusions : — The chromatin and achromatin are not mingled, but 
may be quite separate or more frequently are so disposed that the chro- 
matin encloses almost the whole of the achromatin. What is called the 
nucleolus is due to the separation, within a vacuole, of several micro- 
somes, which usually fuse into one globule. This may be the final stage 
(telophasis) of a preceding division. The central globule unites the 
characters of nucleolus and centrosome. Like a nucleolus, it is absorbed 
into the achromatin substance at the end of division, and regenerates in 
the two daughter-nuclei ; like a centrosome, it condenses substance 
around itself in the form of a small intranuclear attractive sphere, which 
does not pass into the protoplasm to act like an ordinary centrosome in 
division. The mixed character of this globule justifies the opinion of 
those who make no fundamental distinction between nucleolus and 
centrosome, but regard these as homologous structures varying in func- 
tion according as they remain intranuclear or become intraprotoplasmie. 
The absence of external centrosome, and consequently the non-formation 
of an achromatin nuclear spindle, render nuclear division in Spirochona 
peculiar. But in the precocious disappearance of the nucleolus, in the 
production of uniting filaments between the two new chromatin masses, 
and in the formation of a rudimentary cellular plate it has the characters 
of a mitosis. The so-called terminal plates are accumulations of 
achromatin which assist in reproducing the resting nucleus. Centrosome 
and microcentrum are liberated microsomes of chromatin, which pass 
from the nucleus to play an active part in division. 
Ciliated Infusorians in the Horse’s Caecum.f — Dr. A. Bundle de- 
scribes these at length, viz. Cycloposthium (g. n.) bipalmatum Fiorentini, 
Blepliarocorys (g. n.) uncinata Fiorent., B. valvata Fiorent., B. jubata 
* Ann. d. Microgr., vii. (1895) pp. 289-312 (1 pi.). 
f Zeitschr. f. wiss. Zool., lx. (1895) pp. 284-350 (2 pis.). 
