INVERTEBRATE ANIMALS; 



INVERTEBRATA. 



E now come to the second great division into which all animated beings have been 

 distinguished. All the creatures which we have hitherto examined, however 

 different in form they may be, the ape and the eel being good examples of this 

 external dissimilarity, yet agree in one point, namely, that they possess a spinal 

 cord, protected by vertebrae, and are therefore termed Vertebrated animals. 



But with the fishes ends the division of vertebrates, and we now enter upon 

 another vast division in which there is no true brain and no vertebrae. These 

 creatures are classed together under the name of Invertebrated animals ; a somewhat insuffi- 

 cient title, as it is based upon a negative and not on a positive principle. Whatever may 

 be its defects, it has been too long received, and is too generally accepted to be disturbed by a 

 new phraseology, and though it be founded on the absence and not the presence of certain 

 structures, it is concise and intelligible. 



Numerous as are the species of the vertebrated animals, those of the invertebrates out- 

 number them as an army outnumbers a company. Although many species of mammals, birds, 

 reptiles, and fishes, are at present known to science, and the yet unrecognized species are 

 necessarily extremely numerous, there is some hope of obtaining an approximate calculation of 

 their respective numbers. But with the invertebrates, any approach to a census even of known 

 forms is well-nigh impracticable ; and as it is evident that the ocean alone contains within its 

 fathomless depths myriads of beings as yet hidden from mortal eyes, the reader may conceive 

 the utter impossibility of offering the slightest conjecture respecting their numbers. 



SOME EARLY REMINISCENCES BY THE AMERICAN EDITOR. 



THE study of invertebrate forms in America is of so recent an occurrence that there are 

 a number now living who remember that, with the exception of the mollusks or "shell- 

 fish," forty years since the student had but the merest fragment of recorded knowledge 

 to aid him. 



At that time the four great classes of Cuvier were recognized as the legitimate foundations 

 of classification : the two great primary divisions being Vertebrata and Invertebrata those 

 having an internal bony skeleton, and those having none. At this time, even in the immediate 

 vicinity of the Massachusetts metropolis, he was a wise person, beyond the "general," that 

 had a definite idea of the nature of the very few actinias then known on our coast. The entire 

 amount of knowledge, even with those who recognized them when seen, amounted only to the 

 vague term "animal flowers." That they were animal forms, our few science-reading folks 

 had learned from the science news and gossip that was wafted over from the more scientific 

 centres of England and the continent. 



The great branch that embraces the Shell-fish technically the Mollusca had through 

 various causes become, to a certain extent, familiar. Our clams and oysters were certainly 



