ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
189 
and Echinus being all included. The Spatangoida contain the two sub- 
orders of Cassiduloidea, and Spatangoidea. A useful explanation of the 
terms used is appended to the paper. 
Ccelenterata. 
Development of the Septa in Pteroides.* * * § — Herr G. von Koch 
describes two stages in the development of Pteroides spinulosus. The 
longitudinal septum arises from the central fusion of the most oral pair 
of radial parietes. They cease to lie radially, and come to lie in a 
straight line. The cells of the septum probably originate from the 
ended erm, but the relation of septum to oesophagus admits of their 
ectodermic origin. The cavity of the larva is divided by the septum 
into two portions, of which one corresponds to the single interparietal 
space between the two radials above mentioned, and the other to the 
remaining seven interparietal spaces. 
Arrangement of Mesenterial Septa in Peachia hastata.f — M. L. 
Faurot finds that there are ten distinct pairs of mesenterial septa in 
Peachia hastata. Twelve of these are large, of equal size, and set round 
the oesophagus ; eight are very small and not fixed to the oesophagus, 
and there are, also, two pairs of directive septa. Below the oesophagus 
the septa may be divided into three groups, which differ in size and in 
their relations to the generative organs ; in those of the first and second 
size the organs appear at the same level, a little below the oesophagus ; 
with the exception, however, of the directive septa where the organs are 
only developed below the unpaired organ. The septa of the third or 
smallest size are sterile for their whole extent. 
Occurrence of Ctenophores throughout the year.J — Prof. W. C. 
MTntosh brings forward evidence to show that Ctenophores may be 
obtained throughout the year. L. Agassiz considered that they were 
generally annual animals, laying their ova in the autumn and then 
dying — the young brood making its appearance in the spring. On the 
eastern coast of Scotland the most abundant Ctenophore is Pleurohrachia, 
and the presence of small as well as large examples shows that the ranks 
are being gradually recruited, as well as by-and-by supplanted, by the 
younger forms. Pleurohrachia seems to spawn in summer and attains a 
maximum size the following year, the adults gradually disappearing 
after shedding their ova ; at no period, however, is the water devoid of 
them, and throughout the greater part of the year small forms are 
mingled with the larger. Beroe is seldom absent. Lesueuria, also, is 
to be found in greater or less abundance throughout the year, being 
another species whose spawning-period appears to be of extended 
duration. 
Eleutheria.§ — Dr. C. Hartlaub has rediscovered the S2>ecies of 
Eleutheria which Claparede described some thirty years ago, and which 
differed essentially from those described by other authors ; he proposes 
to call it E. claparedii. From the account now given it is clear that this 
* Morphol. Jahib., xv. (1889) pp. 646-9 (1 fig.). 
t Comptes Keudus, cx. (1890) pp. 52-4. 
X Ann. and Mag. Nat. Hist., v. (1890) pp. 43-7. 
§ Zool. Auzeig., xii. (1889) pp. 665-71. 
