ABSTRACT
The principal object of the observations described in the present paper was to test the conclusion, at which I formerly arrived, that a process of embryonic fission is of normal occurrence in Cyclostomatous Polyzoa. The process had already been demonstrated in Crisia (15) and in Lichenopora (16), and I am now able to show that the development of Tubulipora1 takes place on essentially the same lines. In the course of these observations it became apparent that the discrimination of the British species of Tubulipora had not been characterised with sufficient precision.
A preliminary note (17) on this subject was published, in which the genus appears as Id monea.
A commencing division of the terminal membrane is indicated on the right side of fig. 1.
Milne Edwards (29, p. 331) believed that it referred to an “Aulopore.”
As has already been pointed out by Lamouroux (25), p. 66.
See his remarks on Flustra seourifrons, Pall., on p. 122 of the, ‘British Marine Polyzoa’ (1880).
Thompson’s name first appeared in 1847. In the same year Reuss (“Foss. Polyparien d. Wiener Tertiärbeckens,” in Haidinger’s ‘Naturwiss. Abhandl.,’ Band ii, Abth. 1, 1848, p. 39) described Defrancia pluma and (p. 51) Diastopora plumula. The former, at any rate, is doubtless a Tubulipora, and is given as a member of this genus by Manzoni (‘Denkschr. K. Acad. Wien,’ xxxviii, Abth. 2,1878, p. 20, sep. copy) ; it has, moreover, a considerable, resemblance to Thompson’s species. The specific names pluma, plumula, and plumosa are similar in meaning, but they are sufficiently distinct in sound. I think there is no practical inconvenience in reviving Thompson’s name, and in a group where the synonymy is so involved it is advisable to retain any name that can possibly be used when it is moderately certain what was originally meant by it.
The colonies can be conveniently removed from the seaweed by prolonged boiling with caustic potash.
Cf. especially Seeliger (38).
The vesicles are very similar to those which have been figured by Durham (‘Quart. Journ. Mic. Sci.,’ xxxiii, pl. 1, fig. 3) in Spatangids.
The term “embryophore” will be used below to denote the structures, in relation with the primary embryo and its derivative secondary embryos, which are on the proximal side of the vestibule. The principal contents of the ovicell are thus the embryophore, containing the embryo and the fertile brown body, the vestibule, and the terminal membrane.
This measurement is taken between the points C and B in the figures on Plate 9.
Cf. Gregory, No. 12, p. 21.
[The microscopical sections which are referred to as T. plumosa are those in which excretory vesicles were discovered in the tentacles; those referred to as T. phalangea are the specimens in which no excretory vesicles were seen in that position. Unless otherwise stated, the discrimination of these two species in sections depended entirely on this character.]
