264 
NOTES AND MEMORANDA. 
significance of the so-callcu ciliated embryos of the sponge, while not 
reconcilable with the proposed metazoic interpretation, becomes 
clearly intelligible on collating these organisms with the unicel- 
lular Protozoa. Eegarded from this position, the identity of the ovate 
aggregation of separate units which constitute the so-called sponge- 
embryo with the similar aggregation of units of the segmented monad, 
afterwards separated and dispersed as swarm-spores, is made apparent. 
This sponge-embryo is in this manner demonstrated to be merely an 
aggregation of swarm-spores held closely bound to one another 
throughout the process of development — a ‘ swarm-gemmule,’ whose 
mission it is, in its aggregate condition, to lay the foundation of a 
composite sponge-stock similar to the one which gave it birth, and 
in manner identical with that individually effected by each motile 
swarm-spore of the solitary monad. 
As a final demonstration of the protozoic nature of sponges, the 
multiplication of these organisms by the production of countless in- 
finitesimal spores after the manner of the typical Monadina, has been 
determined. This spore-formation is brought about through the 
assumption by the matured collar-bearing zooids of a quiescent 
encysted state, accompanied or not by the fusion of two individuals. 
The spores produced by the breaking up into almost invisibly minute 
particles of the entire protoplasmic substance of the encysted zooids, 
are liberated in the substance of the syncytium ; and within this 
matrix each spore develops again through an amoeboid or cytoblastic, 
and then simply flagellate, phase to an adult collar-bearing unit. The 
multiplication of the typical sponge monads or Spongozoa by the 
means of spores represents the constant and normal manner in which 
the growth and extension of the sponge-colony is effected ; the aggre- 
gated masses of individuals or swarm- gemmules, liberated only at 
certain periods, representing a special development for the more 
extensive dissemination of the species.” 
Osmic Acid . — With reference to Dr. Pelletan’s recommendation 
of osmic acid for the purpose of fixing Eotifers, Infusoria, &c., with 
their organs extended (see p. 189), the following note from the August 
number of the ‘ Journal de Micrographie ’ may be quoted : — “ Osmic 
acid is a reagent the emj)loyment of which requires some precautions. 
It is very volatile, its vapour has a very disagreeable odour, is very 
poisonous, very irritating, and may cause serious injuries to the eyes. 
It is found commercially in the form of crystals, in small tubes her- 
metically sealed. The two points of the tube should be broken, and 
the crystals put into a known weight of distilled water. If the 
weight of the tube when empty is deducted from its weight when full, 
that of the crystallized acid is known, and consequently the strength 
of the solution, which can then be diluted with distilled water as may 
be required. The solutions may be preserved in flasks closed with 
sealing-wax, which can be softened by a heated metallic rod at the 
time of use. A little of the solution may be taken out with a pipette, 
and the flask closed again with the sealing-wax. Small quantities of 
the solution can be preserved for immediate requirements in stop- 
pered bottles. 
