SOME FACTS ABOUT FISHES. 
41 
the generic name of the Lampreys, Petromyzon, or Stone-sucker, 
is derived) ; but they also avail themselves of their power of 
adhesion for a less peaceful purpose, attaching themselves in 
this way to the bodies of other fishes, whose flesh they then 
consume by means of their larger teeth attached to the jaws and 
tongue. In this perfect condition, so far as their habits are 
known, the Lampreys must be regarded as decidedly predatory 
fishes. 
The streams inhabited by Lampreys are found to harbour 
another fish of very similar form, which, from its habit of con- 
cealing itself in the sand of the bottom, has long been known as 
the Sand-pride (Pride being a local name for the small river 
lamprey), and, under the generic name of A mmoccetes, regarded 
as a distinct form of the Lamprey family. In general form it 
is like a lamprey ; it is equally destitute of paired fins, and has 
also seven branchial apertures on each side near the head ; but 
the eyes are exceedingly small, deeply seated, and concealed 
beneath the skin, and the mouth, instead of constituting a cir- 
cular suctorial organ, is a horseshoe-shaped cavity, surrounded 
in front by a sort of membrane, and furnished internally with 
numerous slender papillae, but destitute of horny teeth, and quite 
unfitted for attaching itself by suction to any object. The food 
of the Sand-pride appears to consist of minute aquatic organisms, 
obtained from the sand or mud in which it lives. 
The researches of Dr. August Muller first revealed the exist- 
ence of a more intimate relation between the Ammoccetes and 
the Lampreys, than that implied in their belonging to the same 
family, and to nearly allied genera. By observing the small river 
lampreys in the act of spawning and securing the spawn, that 
naturalist was enabled to watch the development of the embryos 
in the eggs, and was rather surprised to find that the young fish 
produced, after growing for a short time, presented all the cha- 
racters of the Sand- pride or Ammoccetes. Subsequently he ob- 
served the transformation of the Ammoccetes into the Lampreys ; 
but the most remarkable point about this metamorphosis is that 
it is comparatively sudden : it is not until the fourth year of its 
existence that the fish passes from the larval to the adult con- 
dition, and the metamorphosis is effected by a series of changes 
taking place rather rapidly, thus reminding us somewhat of 
what occurs in insects, rather than of the gradual modification 
of the Batrachian larvae. From the occurrence of Ammoccetes 
in the fresh waters of various parts of the world where river 
lampreys have been met with, it would appear that this me- 
tamorphosis may be regarded as general throughout the Lam- 
prey family, although as yet nothing seems to be known of the 
transformations (if any) undergone by the Marine Lampreys. 
A minor change, also partially analogous to what occurs in 
