272 DR. A. RATTRAY ON THE ANATOMY, PHYSIOLOGY, 
ance and in the highest activity, and its own range,—a wide one, it is true, as the Table 
shows, and wider, perhaps, than with the majority of terrestrial or marine animals, because 
the range of aqueous is not so great as that of aerial climate, but still well defined, which 
they cannot pass with impunity, and pass only at the cost of impaired vitality and per- 
haps loss of life. 
Notwithstanding the unquestionable existence of ocean climates, and zones of animal 
and vegetable life characteristic of and peculiar to each, and the probability that the 
Firolidæ are not universally scattered, but systematically distributed according to meteo- 
rological laws, different families having their own peculiar range, out of which they are 
seldom found, the great extent of this in the present instance is instructive and goes far 
to show that the marine fauna, and especially the minute and less-developed forms endowed 
with limited locomotive powers like those under consideration, and therefore apt to be 
involuntarily carried hither and thither and from high to low latitudes, or vice versé, by 
winds, tides, and ocean-currents, and thus drifted out of those waters for which their 
anatomical and physiological structure best adapts them, must possess higher adaptability 
to great and sudden physical and climatie changes, especially in the temperature and 
density of the water in which they float, than land animals, which, for obvious reasons, 
are less subject to this casualty. That the Firolidæ possess this power of accommodation 
in a marked degree is evident from the fact that the specific gravity of the Pacific, 
where the above were found, ranged from 10231 near the equator to 1029 in the higher 
latitudes, and its heat from 504° to 83°—a range of no less than 51 of specific gravity and 
327 of Fahrenheit *. : 
The tropics, which Maury has so felicitously termed the “womb” of the sea, is 
undoubtedly the birthplace of perhaps all the above-tabulated forms ; for, though 
sometimes met with in temperate latitudes, it is there we find them most abundant 
(map); and though they are drifted to many parts of the Pacific, and often carried into 
the colder latitudes of either hemisphere by the irresistible ocean currents against which 
their limited natatory powers are unable to contend, we may fairly presume that they 
are not cosmopolite, and cannot exist in every ocean, and in the waters of so many 
different temperatures and densities as that would necessitate; and perhaps we should 
not far err were we to believe that while warm tropical seas are their native home, and 
this the zone in which the most vigorous part of their doubtless brief career is spent, it is 
in the colder regions that those fortunate enough to escape being preyed on end their 
existence. Carried thither, their life of slender tenure gradually ebbs away as their 
originally warm native element cools on reaching high latitudes and enters the chilly 
seas, which possess a very different heat and weight, in which they finally die. The life 
of the Firola or Firoloides may, indeed, be taken as a type of the existence of many of the 
minute and microscopic organisms which have the ever-changing surface waters of the 
ocean as their habitat, whether fitted for warm or cold waters. Conveyed from one ocean 
to another, as the waters of the globe, like its winds, perform their “circuit,” their limited 
life is ultimately ended by static and thermometrie changes in the fluid in which they 
* These were the highest and lowest observed during three voyages between Vancouver Island and Valparaiso, 
those in the Table being for the places indicated. 
