6 Coel. 
CCELENTERATA. 
Morphology, Special and General. 
Hydrozoa. 
The most interesting new Coelenterate described in the year is Micro- 
hydra ryderi , Potts ; Ryder (46). A minute fresh-water Hydroid, ,5 mm. 
X .15 to .175 mm. No tentacles or pedal disc. Asexual reproduction 
occurs by means of a lateral bud which becomes constricted off from the 
parent from above and below, so that it is attached by its side. Colonies 
of two individuals have been observed. The ectoderm is thin, and the 
nematocysts are mainly aggregated at the oral end. The endodermal 
cells are solid at the cleft-like mouth, then for about a third of the length 
of the animal they are large and vacuolated, but are again solid lower 
down. The upper third alone appears to be specially digestive. Micro- 
hydra is thus the simplest known Coelenterate, being little more than a 
sessile planula. [Q/ 7 . Zool. Rec. xxi. Ccel. p. 9, for refs, to the Hydroid 
phase of Limnococlium , with which Microhydra agrees in many respects, 
but with marked differences.] 
Ussow (48) also describes a new form, anl Yiguier (51) gives some 
additional details of the anatomy of the remarkable Medusa, Tetraplatia 
volitans. 
From an observation on Sarsia tubalosa (= Syncoryne sarsii ) Haacke 
(19) regards the fundamental number of the quaternary Meclusce, at 
least of the Craspedota , to be causally conditioned by the lateral budding 
of the Medusa on the polyp. 
Bedot (2-4) continues his researches on the discoid Siphonophores. 
Chun (7), Claus (8), and Fewkes (13) [see also Reproduction] recur to 
the cyclic development of Siphonophorci. 
Actinozoa. 
Erdmann (10) gives some very interesting details concerning the 
anatomy of the Zoanthecc. These forms differ from all other Actinice in 
the fact that new septa can only be produced by the two interseptal pro¬ 
cesses which lie nearest to the ventral directive septa. He defines all the 
genera, Zocmthus, Mammilifera, Epizoanthus, Palythoa, and Corticifera be¬ 
longing to the Zoanthidce , and Sphenopus and one unnamed new genus 
(genus vii.) to the Sphenopidcc. Of the 13 spp. described, only Palythoa 
axinellci is fully named, the others being referred to by numbers. 
Faurot (11) has a note on the symbiosis of Adamsia palliata with 
Eupagurus prideauxi , and on a few points of its anatomy and develop¬ 
ment. 
Fowler (16) commences his researches on the anatomy of the Madre- 
poraria by an account of the structure of Flahelliim pcttagonichum and 
Phodopsammia parallela ; he calls attention to and corroborates von 
Koch’s discovery that the corallum is a product of the ectoderm, and 
deposited outside the embryo. This ectoderm persists in the adult as the 
layer of calycoblasts, to which the continual growth of the corallum is 
attributable. Attention is drawn to the probable taxonomic value of the 
relations of septa and tentacles to the mesenterial spaces. 
Hubrecht (23) describes Echinoptilum macintoshii, g. & sp. nn., which 
