70 



HAllDWICKE'S SCIENCE-GOSSIP. 



[April ], 1SG7- 



yet presenting sufficient differences to deserve dis- 

 tinction. Naturalists, therefore, express this re- 

 semblance and this diversity by grouping them as 

 distinct species of the same "genus." But the 

 lobster and the cray fish, though belonging to distinct 

 genera, have many features in common, and hence 

 arc grouped together in an assemblage which is 

 called a family. More distant resemblances connect 

 the lobster with the prawn and the crab, which are 

 expressed by putting all these into the same order. 

 Again, more remote, but still very definite, resem- 

 blances unite the lobster with the woodlouse, the 

 king crab, the water-flea, and the barnacle, and 

 separate them from all other animals ; whence they 

 collectively constitute the larger group, or class, 

 Crustacea. But the Crustacea exhibit many peculiar 

 features in common with insects, spiders and centi- 

 pedes, so that these are grouped into the still larger 

 assemblage or "province" Articulata, and, finally, 

 the relations which these have to worms and other 

 lower animals, are expressed by combining the 

 whole vast aggregate into the sub-kingdom of 

 Aunulosa. 



If 1 had worked my way from a sponge instead of 

 a lobster, I should have found it associated, by like 

 ties, with a great number of other animlas into the 

 subkiugdom Protozoa; if I had selected a fresh- 

 water polype or a coral, the members of what 

 naturalists term the subkingdom Ceelenterata, would 

 Lave grouped themselves around my type ; had a 

 snail been chosen, the inhabitants of all univalve 

 and bivalve, land and water shells, the lamp shells, 

 the squids, and the sea mat would have gradually 

 linked themselves on to it as members of the same 

 subkingdom of Mollusca ; and finally, starting from 

 man, I should have been compelled to admit first, 

 the ape, the rat, the horse, the dog, into the same 

 class, and then the bird, the crocodile, the turtle, 

 the frog, and the fish, into the same subkingdom of 

 Vertebraia. 



And if I had followed out all these various lines 

 of classification fully, I should discover in the end 

 that there was no animal, either recent or fossil, 

 which did not at once fall into one or other of these 

 subkingdoms. In other words, every animal is 

 organized upon one or other of the five, or more, 

 plans, whose existence renders our classification 

 possible. And so definitely and precisely marked is 

 1 he structure of each animal, that, in the present 

 state of our knowledge, there is not the least 

 evidence to prove that a form, in the slighest degree 

 transitional between any two of the groups Verte- 

 braia, Annulosa, Mollusca, and Co'lenterata, either 

 exists, or has existed, during that period of the 

 earth's history which is recorded by the geologist. 

 Nevertheless, you must not for a moment suppose, 

 because no such transitional forms are known, that 

 the members of the subkingdoms are disconnected 

 from, or independent of, one another. On the con- 



trary, in their earliest condition they are all alike, 

 and the primordial germs of a man, a dog, a bird, 

 a fish, a beetle, a snail, and a polype, are in no 

 essential structural respects, distinguishable. 



In this broad sense, it may with truth be said, 

 that all living animals, and all those dead creations 

 which geology reveals, are bound together by an 

 all-pervading unity of organization, of the same 

 character, though not equal in degree, to that which 

 enables us to discern one and the same plan amidst 

 the twenty different segments of a lobster's body. 

 Truly it has been said, that to a clear eye the smallest 

 fact is a window through which the Infinite may be 

 seen. 



Turning from these purely morphological con- 

 siderations, let us now examine into the manner in 

 which the attentive study of the lobster impels us 

 into other lines of research. 



Lobsters are found in all the European seas ; but 

 on the opposite shores of the Atlantic and in the 

 seas of the southern hemisphere they do not exist. 

 They are, however, represented in these regions by 

 very closely allied, but distinct forms — the Homarus 

 Americanus and the Homarus Capensis, so that we 

 may say that the European has one species of 

 Homarus ; the American, another ; the African, 

 another; and thus the remarkable facts of geo- 

 graphical distribution begin to dawn upon us. 



Again, if we examine the contents of the earth's 

 crust, we shall find in the later of those dcposits } 

 which have served as the great burying grounds of 

 past ages, numberless lobster-like animals, but none 

 so similar to our living lobster as to make zoologists 

 sure that they belonged even to the same genus. 

 If we go still further back in time, we discover in 

 the oldest rocks of all, the remains of animals, con- 

 structed on the same general plan as the lobster, 

 and belonging to the same great group of Crustacea; 

 but for the most part totally different from the 

 lobster, and, indeed, from any other living form of 

 crustacean ; and thus we gain a notion of that suc- 

 cessive change of the animal population of the 

 globe, in past ages, which is the most striking fact 

 revealed by geology. 



Consider, now, where our inquiries have led us. 

 We studied our type morphologically, when we 

 determined its anatomy and its development, and 

 when comparing it, in these respects, with other 

 animals, we made out its place in a system of classi- 

 fication. If we were to examine every animal in a 

 similar manner we should establish a complete body 

 of zoological morphology. 



Again, we investigated the distribution of our 

 type in space and in time, and, if the like had been 

 done with every animal, the sciences of geographical 

 and geological distribution would have attained their 

 limit. 



But observe one remarkable circumstance, that, 

 up to this point, the question of the life of these 



