Dr. Wallich^ on the Polycystina. 
73 
mens in my possession^ as well as from drawings and notes 
taken at the time^ I have, however, been enabled carefully to 
re-examine them and confirm Professor Huxley^s statement. 
But I am still unable to satisfy myself as regards Sphmro- 
zoiim (Mey.) (the Thalassicolla nucleata of Huxley), and 
would rather provisionally refer it to Noctiluca, with which 
organism it was shown by Huxley to assimilate in many of 
its characters.^ 
In the Plagiacanthid(B, or first family of the Protodermata 
— the name of whose typical genus I take from the Plagiacan- 
tha arachnoides of M. Claparede (''Monastb./ 1856, p. 500), 
which is generally identical with Acantkadesmia (MiilL) — 
we have a connecting link between the Polycystina and this 
Order. For, whilst their siliceous skeleton is formed on the 
type of the single-chambered Polycystina, the sarcode body 
presents, in a marked degree, those characters which distin- 
guish the Protodermata. That is to say, in addition to the 
greater degree of differentiation attained by the sarcode, we 
observe a nucleus of large size, protected by a membranous 
and hyaline capsule; surrounding this the granular, some- 
times very brilliantly coloured, endosarc, towards the outer 
portion of which the sarcoblasts are imbedded ; and, finally, 
the nearly colourless ectosarc, in which the sarcoblasts seem 
to occur only during their transit towards the outer world. 
To this family will be found to belong those strikingly curious 
forms in which the tendency to asymmetrical growth attains 
the greatest limit, and which are known under the names of 
Dictyospiris, Stephanolithis, Spongolithis (Ehr.), and Clado- 
cocc'us, Stylocyclia, and Acanthodesmia (Miill.). 
In the Acanthometrina we observe a much more complex 
disposition of the siliceous parts than has heretofore presented 
itself. These consist of a series of symmetrical spicules, dis- 
tinct from each other, but invariably uniting at their bases 
to .constitute the common axis of the organism, which 
is generally, although not invariably, solid at the point of 
union. The spicules, which in most cases take the form 
of ensiform, hastate, or remiform spines, of wonderful sym- 
metry and beauty, and occasionally of great length, are, 
however, solid throughout and never, as supposed by Miiller, 
tubular ; the semblance of tubularity being produced by the 
* Without speaking positively on the point, I may state my belief tliat 
no true Rhizopod is phosphorescent ; and, so far as my observations on this 
head go, it seems probable that phosphorescence does not take place in any 
organisms holding a lower rank in the scale of being than Noctiluca and the 
Entomostraca. Sliould my surmise prove correct, the luminosity or other- 
wise of Sphcerozoum might assist us in arriving at its true relations. 
