190 vixe: YORKSHIRE carbo^'iferous and pekmiax polyzoa. 
The infreqiiency of ovicells on fragments of Carboniferous Poly- 
zoa need not occasion much surprise, when it is stated, by Mr. Waters, 
that out of the large number of Idmonea, about 130 species and 
varieties which have been described, only seven species have been 
noticed as bearing ovicells ; and out of a large list of Hornera, 
seventy-four, I believe, the ovicell is only known in about nine species." 
It will be noticed in both fragments of Hyphasmopora figured 
that there are two openings in the ovicells, one on the apex and tlie 
other on the side ; but in figure 2 the inferior opening is much more 
distinct than in figure 1. Mr. "Waters, in dealing with the ovicells of 
recent Cyclostomata, has a very pertinent remark on these openings, 
and I cannot do better than quote it, more especially as, in the passage 
I have underlined, the remarks of Mr. Kirkpatrick will apply to Car- 
boniferous as well as to recent species. 
The position and nature of the opening of the ovicell is most 
important, often in fact, more so than the sliape of the ovicell. The 
opening is, however, formed after the ovicell is complete, so that 
frequently this important character cannot be made out, and in my 
specimen {Hornera Jissurata, Busk) I could not find any opening, 
but one of the lateral zocecial tubes is much longer than usual, and 
looked as though this change was connected with the fuuctions of 
the ovicell. I therefore wrote to Mr. Kirkpatrick, of the British 
Museum, explaining what I had seen in my specimens, and asked 
him if he would look at those in the Museum. f He kindly did so 
at once, and \vrote that he had examined ten ovicells, and found in 
each instance that the last one or two Zooecia of a series in proximity 
to an ovicell are not only enlarged, but considerably altered in direction. 
In eight instances the tube curved forwards and upwards so as to 
open on the anterior surface. In two, the tubes opened laterally. 
In every case the wide tube is to some extent connate to a Zocecial 
series ; but in some cases the former curves away from the latter in 
such a way as to make the wide tube appear to be part of the ovicell, 
and not a metamorphosed Zooecium."| 
* Ovicells of Cyclos. Bryozoa. Linn. Soc Jour. Zool., vol. xx., p. 27G. 
f Mounted and presented to the Museum by Miss Busk, from her father's 
" Challeng-er " Collection of Idmonea (Hornera) Jissarata, Busk. 
X Op. cit. pp. 276-277. 
