296 Scientific Intelligence. 
Professor Agassiz has made some recent observations on the ova 
and development of a species of Actinia, and has shown that the num- 
ber of tentacles in the young animal is at firs, five; and he has conse- 
quently inferred that this is a typical or normal number for the true 
Actinie. The Actiniv, it should be observed, are identical with the 
ordinary coral polyps in all points of structure, and this number should 
therefore be expected to occur among them. 
But the author has elsewhere shown* that in the Orbicellz the num- 
ber of tentacles is a multiple of 6 or 4. In the Orb. argus, glaucopis, 
six; in the pleiades, hyades, excelsa, annularis, stedlulata, microph- 
thalma, ocellina, twenty-four ; in the stelligera, eighteen. The number 
six is likewise characteristic (perhaps sometimes four and not six) of 
tacles, and the consequent fission that takes place. While those of the 
six series, as far as direct observation has gone, have a fixed limit to the 
number of tentacles,—the even number siz being a limit-number, while 
five may or may not be so.. The multiplication of tentacles as growth 
proceeds, has been shown by the writer to be quite analogous to the 
spiral development of the leaves or petals of a plant; and ‘it is there- 
fore an interesting fact that five should be the number for the unlimited 
spiral, while six is a limited spiral. This is a point, however, which 
direct observation on the young of the fissiparous zoophytes alone can 
fully establish. 
n absence of fission. The former in- 
cludes the Actinide (excluding the Orbicelle, Echinopore, and Phy I. 
lastree), with the Fungide; while the latter embraces—l. the Orbi- 
cellida (the species of the three genera just mentioned) ; 2. the Cyatho- 
phyllide; 3. the Caryophyllide ; 4. the Gemmiporida ; 5. the Zoan- 
thide ; 6. the Madreporide ; 7. the Antipathide. 
The subgenus Orbicella should therefore take the rank of a genus. 
We shall probably find that there are Actinie of both kinds, although 
hitherto not distinguished. 
* See Report on Zoophytes, p. 49, and this Journal [2], iii, 9. 
