270) Mr. J.T. Arlidge on some of the Phases of Development 
croscope, and possessed in its interior several globules about a 
clear nucleus, indicating an aptness for ulterior changes, I deter- 
mined to prosecute a further observation of it. 
Occupying about the centre of the bemg was a distinct, clear 
nucleus*, and around this were arranged six or seven granular 
greenish globules, with mterspersed particles or granules. The 
circumference was also furnished with a single row of long and 
large cilia, which caused the animaleule to rotate on its own axis, 
without altering its relative position (Pl. VII. B. fig. 1). 
After observation had been continued a little while, most pro- 
bably from a change of position of the creature, an interior, con- 
tained circle came into view, eccentric to the outer one so far, 
that an interval was left between the two for about half of their 
periphery, whilst in the remaining half the two spheres were in 
apposition. This interval left between the two had a rather 
darker colouring, owing to its finely granular character, being 
minutely dotted as in engraving (fig. 2). 
These appearances were present about half-past one o’clock P.M. 
Moreover, at the same time that the two circles came under no- 
tice, the inner one was observed to rotate independently of the 
outer one, and indeed in the contrary direction,—a result I believe 
due (judging however from some slight indications only) to its 
surface being clothed with delicate cilia. Thus, the cilia of the 
external tunic bent themselves to the left+, producing a motion 
from right to left, whilst the inner one revolved turning from 
left to right. This contrariecty in the direction of the revolution 
of the two spheres was very observable, being, at this period and 
for some time afterwards, very active. 
In process of time the motion of the contaimed circle waxed 
more rapid than that of the external, and seemed to impede the 
latter; at least, the rotation of the outer sphere became irre- 
cular, and was altogether slower than when first witnessed. 
Between two and three o’clock the number of included glo- 
bules had decreased ; and instead of six or seven about the pellucid 
nucleus, only four could be discovered, but these were of larger 
size than those heretofore noticed. One of the four seemed more 
eranular than the rest, and deeper seated ; another, of the largest 
size, had one-half of its cavity clear, the other ‘occupied with 
green granular matter. The remaining two were tolerably clear. 
Scattered in the imterspace between the vesicles were some 
rounded granular green masses about one-fourth the size of the 
former, and, in addition, the common formless green particles 
(fig. 3). 
* This nucleus would, according to Ehrenberg’s ideas, be called the testis 
or sperm-cell. 
+ I speak here of the apparent directions assumed, viewed under the mi- 
croscope : hence the real directions are just the reverse. 
