1864.] DR. A. GUNTHER ON A POISONOUS FISH. 157 
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 lines 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-organs, 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, 
can only be effected by the pressure to which the sac is subjected 
the moment the spine enters another body. 
Nobody will suppose that a complicated apparatus like the one 
described can be intended for conveying an innocuous substance, and 
therefore I have not hesitated to designate it as poisonous; and the 
greatest importance must be attached to it, inasmuch as it assists us 
in our inquiries into the nature of the functions of the muciferous 
system, the idea of its being a secretory organ having lately been 
superseded by the notion that it serves merely as a stratum for the 
distribution of peripheric nerves. Also the objection that the Sting- 
Rays and many Siluroid fishes are not poisonous, because they have 
no poison-organ, cannot be maintained, although the organs con- 
* 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. 
