PROCEEDINGS OF SOCIETIES. 200 
persuaded himself that he had actually seen the reputed worms 
moving about. 
Dr. Alexander Dickson exhibited some very interesting pre- 
parations, showing in various stages of development the pair of 
curious root-like temporary appendages, emanating from the base 
of the suspensor in Tropeolum. 
21st March, 1867. 
Dr. E. Perceval Wright exhibited the spicules of Hyalonema 
and Euplectella, and pointed out their resemblances and differ- 
ences, comparing them also with examples of known sponges. 
Dr. Collis showed a section of a bony tumour as an opaque 
object ; the concentrically arranged layers and wide cavities, very 
like Haversian canals, of this porous substance, could be well 
seen, as well as certain grooves in which blood-vessels had lain. 
It differed from true bone in the irregular arrangement of these 
canals and in their varying size, also in the lacune being almost 
absent, and the canaliculi very small. The tumour from which 
these sections were made was of thirty vears’ growth. 
Mr. Crowe showed fine specimens of Gdogonium tumidulum, well 
showing the antheridia and nascent oogonia. 
Rev. E. O’ Meara exhibited specimens of a Diatom, the type of a 
new genus, which he named Ptychodiscus, and the species Pty- 
chodiscus lineatus, fromthe Arran gathering ; a description and 
figure of which is to appear in this Journal. 
Dr. John Barker exhibited a parasitic growth on Didymopriwm 
Grevillii, which appeared somewhat akin to that he drew atten- 
tion to at the January meeting; but in this instance the filaments 
were not curved but erect and straight, and gave off slender and 
numerous branches at the apex. The stem, so to call it, was 
rather thinner at the base than at the summit, and seemed to hold 
imbedded in it a single series of colourless globular bodies. 
When two or several of these growths occurred near each other 
the branches of one often leaned towards those of a neighbour, 
and they became mutually entangled. 
Mr. Archer showed specimens and drawings of the various 
stagesof the development and of the perfect zygospore of Spirotenia 
condensata (Bréb.), especially interesting as being the first recorded 
instance of the fructification in this pretty species (the position 
of the genus remaining hence doubtful) as well as presenting the 
characteristic of being externally surrounded not by spines of any 
fashion, but by a honeycomb-like structure. The zygospores are 
moreover double or ¢win, each pair of parent conjugating cells, 
by a preparatory separation of the contents into two portions, 
giving origin to a pair of zygospores, in which respect there is a 
parallelism in Closteriwm Ehrenbergii and Closterium lineatum. 
Inasmuch as a detailed account of the conjugation and of the 
zygospores, with figures, appears in the present number of this 
Journal, it becomes unnecessary to enlarge upon them here. 
