1(38 
Transactions of the Society. 
V . — On Fucitrogus Rhodymenisc , a Gall -'producing Copepod. 
By G. S. Brady, M.D., LL.D., F.B.S. 
( Read 21s£ February , 1894.) 
Plate V. 
Some time ago, Miss Ethel S. Barton described certain malformations 
or galls which she had found upon various marine algae* — Rhodymenia 
palmata Grev. , Ascophyllum nodosum , and Desmarestia aculeata Lin. — 
and she was kind enough to send me specimens of some Entomostraca 
(Copepoda) which occurred in the cavities of the galls. Some of these 
belonged to well-known free-swimming species whose association with 
the galls must be looked upon as purely accidental, but there were 
others of an unknown type, and quite abnormal in structure, which 
I believe to be the active agents in the production of the Rhodymenia 
galls, and which I propose here to describe. In the outgrowths of 
Ascophyllum , Miss Barton records that she found numerous specimens 
of a nematoid worm, which Dr. de Man, of Middelburg, believed to 
be undescribed, and which is presumably the cause of the galls in that 
plant. It would appear, therefore, that there is a large and extremely 
interesting field open for investigation in this direction. 
I have as yet had no opportunity of seeing the living animal of the 
Rhodiymenia gall, and the few specimens sent to me by Miss Barton 
have not sufficed to render the structure altogether clear. An exami- 
nation of the living animals would, doubtless, do much to elucidate 
many points which are now obscure. Yet, from what has been made 
out, I see little reason to doubt that the creature is a permanent 
inhabitant of the gall-cavity, and that the gall is probably produced 
by it. I have come to this conclusion for the following reasons : — 
First, the shape and generally degenerate condition, which are those 
characteristic of many parasitic Crustacea ; secondly, the apparently 
suctorial character of the mouth ; thirdly, the build of the mouth- 
organs, which approach more nearly those of some of the Ascidiicolous 
species than to any free-living forms ; lastly, the absence of any 
appendages adapted for creeping or swimming. 
As this species cannot be placed under any of the three sections 
(Gnathostomata, Poecilostomata, Siphonostomata) which, following 
EXPLANATION OF PLATE V. 
Fucitrogus Rhodymenix, magnified 110 diameters. 
a, mandible. &, antennule. c, antenna. 
d, mandible-palp (?) e, maxilla-palp (?) /, maxilla (?) 
g, maxilliped with setae ( h ) and tentacular cirri ( i ). 
k, papilla with genital aperture. 1 1. setae. 
ph, pharynx, st, stomach. 
* “ On the Occurrence of Galls in Rhodymenia palmata Grev.,” Journ. of Botany, 
March 1891. “On Malformations of Ascophyllum and Desmarestia Murray’s 
Phycol. Memoirs, 1892. 
