88 REPORT—1868. 
who, recognizing its hydroid relations, placed it in the genus Sertularia under the 
name of S. arcta. 
It was afterwards described by Dr. Hassall, who insisted, with reason, on its 
claims to constitute the type of a new genus, to which he gave the name of 
Coppinia. 
The Coppinia arcta is now familiar to every student of the Hydroida, but some 
of the most interesting points in its structure have been entirely overlocked, and 
we do not possess even a correct diagnosis of its genus. 
The two principal portions which, even on a superficial inspection, are seen to 
enter into the composition of the hydroid have been recognized by Dalyell and 
others. These consist (1) of a continuous basal incrusting portion, and (2) of more 
or less curved cylindrical tubes, which project from the free surface of the incrust- 
ing portion. It has further been shown that these tubes contain each a hydranth 
provided, in some cases at least, with a verticil of tentacles surrounding the base 
of a short hypostome, and in such cases capable of protrusion from the tube and 
of retraction within it. The tubes are thus true hydrothecwe. The hydvanths are 
conspicuous by their fine lemon-yellow colour. 
The incrusting base, however, has been entirely misunderstood, and yet its 
structure is full of interest. The hydrothecal tubes can be traced through it to 
its attached surface, while vertical and transverse sections show that the rest of 
the crust is composed of vertical chitinous tubes rendered polygonal by mutual 
pressure. They adhere to one another by their sides, and each opens on the frce 
surface of the crust by a small circular orifice, which had been already pointed out 
by Dalyell. 
These tubes are true gonangia. Within each isa solitary gonosac which buds 
apparently from a blastostyle, which, however, has been more or less suppressed 
by the growing gonosac. A sufficiently obvious spadix may be recognized in the 
gonosac, and between it and the walls of the female gonosac lies a sinele large 
Iemon-yellow oyum. In this oyum, during its earlier stages, may be seen a di- 
stinct germinal vesicle, in which the place of the germinal spot is occupied by 
numerous Clear spherical bodies, which disappear in a few seconds after the ovum 
is liberated from the gonosac and exposed to the influence of the surrounding 
water. 
Segmentation commences while the ovum is still within the gonosac, and the 
ovum becomes thereby converted into a granular plastic mass, which is now forced 
out through the orifice in the summit of the gonangium. It carries out with it, 
however, a hernial extension of the attenuated walls of the gonosac, which form 
for it an acrocyst, in which it remains still for some time confined. It ultimately, 
by the rupture of the acrocyst, escapes as a planula into the surrounding water. 
The planula and its development into a hydranth included in a chitinous tube 
have been observed by Dalyell. 
Both hydrothece and gonangia spring from an adherent tubular and anasto- 
mosing fibre, without the intervention of a distinct hydrocaulus. 
A knowledge of the structure of Coppinia acta will enable us to give a more 
correct generic diagnosis than was possible as long as we were ignorant of the true 
nature of this curious hydroid. The following may be taken as expressing the 
essential characters of the genus :— 
Trophosome.—Hydrocaulus absent; hydrothecse tubiform, sessile upon an ad- 
herent retiform hydrorhiza, and haying their proximal extremities plunged into 
the mass of the incrusting gonosome ; hydranths with a single verticil of filiform 
tentacles. 
Gonosome.—Gonophores adelocodonic ; gonangia tubiform, forming by the ap- 
proximation of their sides a continuous incrusting mass surrounding the bases of 
the hydrothecx, which emerge from it at intervals. 
On the Occurrence of Erysimum orientale under peculiar circumstances at 
Edinburgh. By Professor T. C. Arcumr. 
This plant was found during the present year in a garden situated in the Old 
Town of Edinburgh. The circumstances attending its appearance were remarkable. 
