486 
POPULAR SCIENCE REVIEW. 
which I have made in another place, on the psychical pheno- 
mena legitimately inferrible from this minute animal’s pro- 
ceedings : — 
“ It is impossible to witness the constructive operations of 
the Melicerta without being convinced that it possesses mental 
faculties, — at least if we allow these to any animals below man. If, 
when the chimpanzee weaves together the branches of a tree to 
make himself a bed ; when the beaver, in concert with his 
fellows, gnaws down the birch saplings, and collects clay to 
form a dam ; when the martin brings together pellets of mud 
and arranges them under our eaves into a hollow receptacle for 
her eggs and young, — we do not hesitate to recognize m ind — 
call it instinct or reason, or a combination of both, — how can we 
fail to see that in the operations of the invisible animalcule there 
are the workings of an immaterial principle ? There must be a 
power to judge of the condition of its case, of the height to 
which it must be carried, of the time when this must be done ; 
a will to commence and to go on, a will to leave off (for the 
ciliary current is entirely under control) ; a consciousness of the 
readiness of the pellet, an accurate estimate of the spot where 
it needs to be deposited (may I not say also a memory where 
the previous ones had been laid, since the deposition does 
not go on in regular succession, but here and there, yet so as to 
keep the edge tolerably uniform in height?), and a will to 
determine that there it shall be put. But, surely, these are 
mental powers. Yet mind animating an atom so small that 
your eyes strained to the utmost can only just discern the speck 
in the most favourable circumstances, as when you hold the glass 
which contains it between your eye and the light, so that the 
ray shall illumine the tiny form while the background is dark 
behind it ! ” 
This prettly little builder is very common on most of our 
pond-weeds,and when it does occur, a good many are generally 
found in close proximity.* I have had them swarming to such 
a degree that sixty or seventy were crowded on a single small 
leaf. An adult will measure l-20th of an inch in height, of which 
the case may be l-24th of an inch. Such a case contains about 
thirty or thirty-five horizontal rows or courses of pellets. Each 
pellet is surrounded by six others ; they are set in uninter- 
rupted perpendicular lines ; but those of one horizontal row are 
made to alternate with those above and below it, just as bricks 
are ordinarily set in a wall. Each naturally-made pellet, exa- 
* Dr. Mantell (“ Thoughts on Animalcules,” pi. iv.) has figured an adult 
M. ceratophylli, with seven young, each with a well-formed case, adhering to 
various points of the parental case. I have never met with such an example 
as this, hut have seen one case attached to an older one. 
