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POPULAR SCIENCE REVIEW. 
a similar set of seven “stigmata” on either side, they com- 
municate internally with a median canal, which ends blindly 
behind, but runs forward beneath, and totally distinct from 
the gullet, to communicate with the pharynx through the 
medium of a valve-guarded opening. 
The above curious modifications of the breathing apparatus 
have an evident relation to the pre-occupied state, so to speak, 
of the mouth in the fishes under consideration ; that of the 
Hag being commonly buried in the flesh of its “ host,” while 
that of the Lamprey, if not similarly engaged with prey, serves, 
suckerwise, to anchor its waving owner to some stone or other 
support.* 
A delicate cartilaginous trellis-work — the parts of which, 
according to Mr. Mivart, are not homologous with the branchial 
arches of bony fishes — surrounds the branchial apertures in the 
Lamprey, and, moreover, in some degree encases and protects 
the heart.f 
The leading varieties of all bona-fide fishes having been passed 
in review, only two somewhat aberrant forms, which occupy 
positions on the boundary line of the class, or, one is almost 
tempted to say, the topmost and lowest rungs respectively of 
the fish-ladder, claim, in conclusion, some slight notice. To 
begin with the lowest form, viz., the Lancelet ( Amphioxus ). 
This little fish, which seems to be the very roughest sketch 
of a vertebrate animal, with a brainless nerve-system, blood- 
vessels which lack a heart, and a backbone devoid of vertebrae, 
respires in this wise : water is taken in at a mouth surrounded 
with fringes, and, after passing, gently urged along by cilia, 
through windows — between the panes of which are pulsatile 
vessels — perforated in the pharynx, into a cavity answering to 
a branchial cavity, finds its exit by an orifice pierced through 
the ventral surface of the fish. 
The mechanism of respiration here seems almost identical 
with that in animals a little lower than the Mollusca, namely, 
the Ascidia, or “ sea-squirts” (see Popular Science Review , 
July, 1869), creatures which, according to recent researches, 
seem, in early stages of development, to make somewhat startling 
approaches to animals once thought to be separated from them 
by an impassable gulf and by well-defined barriers. 
* It is stated in one of the Hunterian catalogues ( Physiology , vol. ii. 1029) 
in the Royal College of Surgeons, that if a Lamprey, when sticking to the 
side of a vessel, u he held with one series of apertures out of the water, the 
respiratory currents are seen to enter by the submerged orifices, and, after 
traversing the corresponding sacs and the pharynx, to pass through the op- 
posite branchia and to be forcibly ejected therefrom by the exposed orifices.” 
t Preparation 34, Royal College of Surgeons. 
