i32 
j. D. SIDDALt. 
Size , — The first specimen observed measured in length of 
body, without the pseudopodia, *07 inch (1*75 millim.), and 
in breadth *0016 inch (0*042 millim.). Since then I have 
measured a number of others, the largest of which is *31 inch 
(7*5 millim.) in length, and *2 inch (0*5 millim.) in breadth. 
The rest vary between these two extremes. (PI. XV, fig. 1.) 
Two days after finding the first I observed a second much 
larger specimen, and examined it carefully whilst living with 
powers varying from 280 to 800 diameters (^ in. objective 
with A to D eye-pieces). Nothing fresh was noticed in the 
sarcode, except that it contained, in addition to the dark 
granules of irregular size and shape, a considerable number 
of spherical and oval masses, relatively larger in size, of clear 
colourless protoplasm. These were carried along by the 
rotating current, but did not travel so quickly as the finer 
portion of the sarcode, probably owing to their greater size 
and weight. No traces of a contractile vesicle could be seen 
although carefully sought for. Neither structure nor surface 
markings of any sort could be discerned in or upon the in- 
tegument, which presented a perfectly homogeneous texture, 
and may therefore be regarded as a simple layer of hardened 
or otherwise slightly modified protoplasm. 
The nucleus proved to be a far more difficult subject for 
study, but careful observation in upwards of twenty examples 
has within the last few weeks revealed its structure. Ex- 
amined in the living state very little can be made out satis- 
factorily. In appearance it is a simple oval sac or cell 
possessing a wall of exceeding tenuity, and filled probably 
with fluid of greater transparency than the sarcode which 
surrounds it. The chief difficulty arose from certain dark 
lines, continually travelling over its surface ; not ceasing 
either when the nucleus was carried along with the rotating 
sarcode, or momentarily arrested. Some of the varying ap- 
pearances thus presented are shown in PL XV, fig 4. After 
watching these lines for many hours I was led to attribute 
them to alternate wrinkling and distension of a nucleus- 
membrane, taking place without any regularity as to time. 
They appeared generally to open out from the centre to the 
edges of its longer diameter, or vice versa. This seemed to 
prove definitely the existence of a distinct wall of greater or 
less resistance coating the nucleus, and it appeared to me 
that whilst the lines were chiefly the result of the unequal 
external pressure of the impinging currents of sarcode, they 
might also be in some degree due to inherent causes ; and 
continued observation has led me to believe that the latter 
rather than the former is the correct explanation. 
