GENERAL NOTES. 
439 
than the 6 ordinary arms), while in some species of Linckia and Ophidiaster 
a radiary division takes place, every single arm regenerating the whole set 
of arms from its proximal end. (In Asterias helianthus the number of arms 
is constantly increasing through the intercalation of new arms.) The cir- 
cumstances attending these curious facts are given in detail, and comparisons 
instituted with the phenomena of regeneration and division in other Itadiata. 
The connexion between spontaneous division, regeneration, and gemmation is 
critically discussed; it is pointed out that the so-termed “spontaneous divi- 
sion ” is in many instances (Strohila, Infusoria, and probably also the fissi- 
parous Annulatd) not a division, but a more or less masked gemmation ; so 
that the existence of a true self-division beyond the limits of the unicellular 
organisms {Momra &c.) might be doubted, were it not that the fissiparous 
Starfishes and Brittlestars showed in an unequivocal manner the qualitative 
difference between this monogenetic process and true gemmation. (Kowa- 
LEWSKY, Z. wiss. Zool. xxii. p. 283, confirms Lutken’s observations, from the 
examination of living specimens. The division of Asterias tenuispina is easily 
observed when specimens with all the arms of full length are put in a tank with 
sea- water; on the secondday,if not earlier, they will begin to divide, the 6-armed 
ordinarily into two with 3 arms, the 7-armed into one with 3 and one with 
4 arms, the latter often again subdividing into two with 2 arms. (Greeff’s 
observations [11, p. 104] intimate that external circumstances may influence 
the process.) This division was also observed in a small “ Opliiolepis ” [pro- 
bably Ophiactis Virens'] in the Bay of Naples. In Linckia ehrenhergi (in the 
Red Sea) the arms will separate from the body quite regularly, one after the 
other, and the severed arms will reproduce 4 arms from the proximal end 
\cf. woodcuis, p. 123, in Lutken’s paper]. Not a single specimen could be 
found with all the arms regularly developed.) Liitken sums up the result of 
the whole discussion on spo'ntaneous division in Echinodermata ^ndiAnthozoa 
thus: — 1. Bivisibility is the highest expression of the rogonorativo power in 
animals; 2. In certain Radiata endowed witli a very liigh rogonorativo faculty, 
spontaneous division occurs alone (Asteridee, Ophiurida;) or combined with 
gemmation (Actinice) ; 3. The true self-division or schizogenesis in Actinim, 
Medusce, Asteridee, and Ophiuridee (not to be confounded with the masked 
blastogenesis in Infusoria, ScypMstoma, and certain chaetopodous Annulata') 
ought to be regarded as a distinct type of asexual reproduction (monogenesis), 
on the same lino as blastogenesis, sporogencsis, and parthenogonesis. 
< Geographical Distribution. 
Grube enumerates the Echinoderms observed at Roscoff and St. Malo 
(Abb. schles. Ges. 1868-69, p. 128; 1860-72, p. 143 ; Echinus miliaris is erro- 
neously treated as a Spheer echinus], Fischer (9) enumerates 26 species from 
the west coast of France ; 22 of these are Mediterranean, and 6 of them find 
their northern and 4 their southern limit somewhere in this region. Some 
biological facts are recorded, as is also the case with Lafont’s list of species 
observed at Arcachon (Act. Soc. L. Bord. xxviii. p. 278: Asterias ruhens — 
viotacea, ^ ). Compare also the preliminary notes of Fischer and Folin on 
results obtained by dredging off Cape Breton : C. R. Ixxiv. pp. 750-753. 
Metzger adds Astropecten muelleri to his previous list of the Echino- 
derms of the shore of Ostfriesland (Die wirbellosen Thiere der ostfriesischen 
