TRANSACTIONS OF THE SECTIONS. 71 
motion, and which are most probably spermatozoa. The ova-like bodies are there- 
fore true ova, and the bodies developed from them (sometimes polypoid embryos, 
but most frequently resembling the “Planule” of Sir J. G, Dalyell) are the product 
of a true sexual process, and not, as has been asserted, mere gemme or bulbille. 
In the Sertularide medusoid bodies have been witnessed by many observers to 
escape from the “ ovarian vesicles” of Campanularia, and swim freely away ; while 
Loven and Lister have observed similar though less completely developed medusoids 
expand at the mouth of the vesicles of this genus, discharge their ova, and then 
wither away without ever becoming free. Besides these gemmez of obvious medusoid 
organization, certain more or less globular bodies are commonly seen in the interior 
of the vesicle clustering round the fleshy axis, and described by various observers as 
eggs. In these so-called eggs of the Cumpunularie, however, the author has de- 
tected a medusoid structure quite as manifest as in 7ubularia. Each of them is in 
fact a fixed Medusa, either developing within it true ova which present a distinct 
germinal vesicle and germinal spot, and undergo the process of yelk-cleavage, when 
they finally escape as “‘ Planulz ;’’ or else, as it would appear in some cases (though 
this will require further observations for its confirmation), containing spermatozoa. 
Among the Sertularine no case had hitherto been observed of the production of 
anything resembling Medusa-buds, The author has however found the axis de- 
veloped in the interior of the ‘‘ ovarian vesicle’ of Sertularia argentea into a medu- 
* soid body, which, though permanently fixed, presented medusoid structure more 
highly developed than in the fixed sacs of the Campanularie and Tubularide; the 
peduncle of this Medusa terminated by an open mouth, and the disc was also 
open; the gastro-vascular canals were present; the ova appeared to be developed 
in.the walls of the peduncle. 
The facts recorded in the present communication were believed by the author to 
be the only ones wanting to harmonise the singularly discrepant observations of the 
several trustworthy zoologists who have made these polypes their special study. 
By a careful collation of these facts, and those already established by independent 
observers, the following conclusions may be obtained :— 
1. That the Tubularian and Sertularian Polypes are in their young state either 
“ Planule ” or solitary naked polypoid larve (“ Actinule’”’). 
2. That both “ Planule ”’ and “ Actinulz ”’ are embryos proceeding from real ova, 
the result of a true sexual process. 
3. That these ova are produced in all cases by a proper medusan structure, how- 
ever masked this structure may be under the form of a fixed ovisac. 
4. Thatthe free medusoids are not embryos, but buds, and that they are destined, 
probably in all cases, as we know them to be in some, to produce ova by a true 
sexual process in a manner similar to what takes place in the fixed sacs. 
5. That every ? species of the Tubularide and Sertularide therefore produces by 
gemmation two kinds of polypes, one hydroid and destined for nutrition, the other 
medusoid and destined for sexual reproduction. 
6. That the medusoid polypes are either fixed or free, the fixed with a more or 
less masked medusoid structure discharging their ova in the immediate vicinity of 
the parent stock ; and the free with a highly developed medusoid structure and fur- 
nished with active powers of locomotion, by which they are enabled to carry their 
- ova to a distance, and thus provide for the diffusion of the species. 
On the Significution of the Ovigerous Vesicles in the Hydroid Polypes. 
By Professor ALLMAN, M.D. 
On a singular Locality chosen for its Nest by the Black Red-Start (Sylvia 
Tithys). By Martin Barry, U.D., F.RS. 
At the railway station in Giessen, Hesse Darmstad:, in May 1852, it was found 
that a bird had built its nest on the collision spring of a third-class carriage which had 
remained for some time out of use. The bird was the Black Red-start (Sylvia Tithys) ; 
and the nest contained five eggs. The discovery was made by the ‘‘ Wagenmeister,” 
Jacob Stephanij, who humanely desired his men to avoid as long as possible the run- 
