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PROFESSOR E. RAT LANKESTER. 
of being retained as a covering for a definite period, the 
secreted material is soon abandoned by the organism, and thus 
these ghostly sketches of the Archerina are left empty and 
useless. They may be compared to the numerous cellulose - 
chambers secreted and rapidly abandoned by the protoplasm of 
Archer’s Chlamydomyxa. They are remarkable inasmuch as 
they show that the whole surface of the protoplasm of Arche- 
rina can secrete a skeletal product. Not only the delicate 
layer of protoplasm which invests each chlorophyll-corpuscle, 
but also the filamentous pseudopodia as far as their delicate 
extremities secrete this skeletal investment. The secretion 
of a skeletal investment by filamentous pseudopodia is unusual. 
It is known to occur in such oceanic Thalamophora as Glo- 
bigerina, where the investment is calcareous, and in some 
Radiolaria (Tripylsea) where it is siliceous (hollow spicules). 
A membranous investment secreted by pseudopodia is, I 
believe, hitherto unobserved. The Heliozoa are known to 
obtain a certain stiffness and permanence for their filamentous 
pseudopodia by the secretion of an axial horny filament. 
Here we seem to have evidence of a capacity for strengthening 
and stiffening the radiant pseudopodia, by the development of 
an external skeletal tube of a similarly horny (membranous) 
nature. 
As to how the living matter recedes from the investment 
which it has formed so as to leave these empty cases, I have no 
suggestion to offer. And I am not able to assert, although it 
seems to be unlikely, that the removal of the living matter 
from within these ghostly skeletons may not be due to the 
death and decomposition of the living matter. In any case, 
these skeletal residues of Archerina-colonies are amongst the 
most interesting and characteristic of the features presented by 
this organism. 
5. Physiological Observations. — The protoplasm of Archerina 
in all the phases here recorded was extremely sluggish. I did 
not detect any streaming movement in it in any case, nor any 
change of form which could be followed with the eye. In the 
Actinophryd-phase I failed to observe any evidence of the 
