470 THE POPULAR SCIENCE MONTHLY, 



of one segment, or cell, type of both the ccelenterata and molluscoicla 

 of Mr. Huxley, and of all mono-segmental creatures. 



Henceforward, this type is the unit of animal organisms, as a sim- 

 ple cell is the unit of primary vegetal life. For want of a better term 

 such a creature may be called a mono-segmentarj^, consisting of but 

 one segment or imit ; while all otliers are polysegmentarian — consist- 

 ing of more sections than one. 



Nature retains her habits very tenaciously. If we haA'e seen her 

 rising to higher and higher types of vegetal structure by adding cell 

 to cell ; duplicating cells by division and holding on to them by adhe- 

 sion ; extending them by increase upon one axis into a baculus ; upon 

 two axes into thalli ; and folding them again into fronds, leaves, and 

 fruit — we no less see her handling this new unit of organization in a 

 similar manner. Ay ! the parsimonious huiJcler again goes through pre- 

 cisely the same means of progress. She works by compounding ; by mul- 

 tiplication of segments ; by gemmation ; by the evolution of higher 

 types ; by a failure to expel the simple segments ; until, by adhesions 

 in foetal life, a more comj^lex creature is formed of multiplied powers. 



Here, again, we come to great gulfs and faults in the strata, which 

 naturalists tell us cannot be bridged over. There remain still the 

 three highest types of organic creatures to be accounted for, namely, 

 the annulosa^ or articulata, the moUusca, and the vertehrata. Our 

 most eminent recent naturalists regard all these as unconnected with 

 preceding forms, and unconnected with one another. Some of the very 

 recent, as Haechel, endeavor to show a consistent chain here by connect- 

 ing directly moUuscoids with vertebrates ; dropping out of the series 

 entirely the two great classes of mollusca and articulata, and leaving 

 their evolution unaccounted for. True, there can be no objection to 

 leaving them out of the chain, if they have no place in it. If we can 

 arrive at vertebrates and man directly from the holothurius, well and 

 good. It would be analogous to other proceedings of Nature, as in the 

 separate evolution of the whole grand vegetal kingdom from the first 

 living germs, in a direction exactly opposite, as it were, to animal evo- 

 lution. But we should also account for the genesis of the two eccentric 

 classes, and connect them in some way with primordial types. 



COLOK IX AXBIALS. 



^T^HE variety of coloring in animal life is one of the marvels of Nature, 

 J- only now beginning to be studied scientifically. It is vain to say 

 that an animal is beautiful, either in symmetry or diversity of color, 

 in order to please the human eye. Fishes in the depth of the Indian 

 seas, where no human eye can see them, possess the most gorgeous 

 tints. One thing is remarkable : birds, fishes, and insects, alone possess 



