460 Zoological Society. 



The structure of the poisou-organ is as follows : — 



1 . The opercular part. — The operculum is very narrow, vertically 

 styliform, and very mobile ; it is armed behind with a s])ine, eight lines 

 long, and of the same form as the venom-fang of a snake ; it is, how- 

 ever, somewhat less curved, being only slightly bent upwards ; it 

 has a longish slit at the outer side of its extremity, which leads into 

 a canal perfectly closed, and running along the whole length of its 

 interior ; a bristle introduced into the canal reappears through an- 

 other opening at the base of the spine, entering into a sac situated 

 on the opercle and along the basal half of the spine ; the sac is of an 

 oblong-ovate shape, and about double the size of an oat-grain. Though 

 the specimen had been preserved in spirits for about nine months, it 

 still contained a whitish substance of the consistency of thick cream, 

 which on the slightest pressure freely flowed from the opening in the 

 extremity of the spine. On the other hand, the sac could be easily 

 filled with air or fluid from the foramen of the spine. 



No gland could be discovered in the immediate neighbourhood of 

 the sac ; but on a more careful inspection I found a minute tube 

 floating free in the sac, whilst on the left-hand side there is only a 

 small opening instead of the tube. The attempts to introduce a 

 bristle into this opening for any distance failed, as it appears to lead 

 into the interior of the basal portion of the operculum, to which the 

 sac firmly adheres at this spot. 



2. The dorsal part is composed of the two dorsal spines, each of 

 which is 10 Hues long. The whole arrangement is the same as in 

 the opercular spines ; their slit is at the front side of the point ; 

 each has a separate sac, which occupies the front of the basal portion ; 

 the contents were the same as in the opercular sacs, but in somewhat 

 greater quantity. A strong branch of the lateral line ascends to the 

 immediate neighbourhood of their base. 



Thus we have four poison-spines, each with a sac at its base ; the 

 walls of the sacs are thin, composed of a fibrous membrane, the inte- 

 rior of which is coated over with mucosa. There are no secretory 

 glands imbedded between these membranes, and these sacs are merely 

 the reservoirs in which the fluid secreted accumulates. The absence 

 of a secretory organ in the immediate neighbourhood of the reservoirs 

 (an organ the size of which would be in accordance with the quan- 

 tity of the fluid secreted), the diversity of the osseous spines which 

 have been modified into poison-organ«, and the actual communica- 

 tion indicated by the foramen in the sac lead me to the opinion that 

 the organ of secretion is either that system of muciferous channels 

 which is found in nearly the whole class of fishes, and the secretion 

 of which has poisonous qualities in a few of them, or at least an in- 

 dependent portion of it*. 



The sacs are without an external muscular layer, and situated imme- 

 diately below the loose thick skin which envelopes the spines to their 

 extremity ; the ejection of the poison into a living animal, therefore, 



* This, of course, must be demonstrated by further preparations; for I 

 would not sacrifice the single (typical) specimen, the less as we may confidently 

 hope that Capt, Dow will furnish us with ample materials before long. 



