lOO NATURAL SCIENCE. February. 



(lo). All these new forms of life arising out of that highly plastic 

 form, the Chaetopod Annelid, were, I believe, due not to the selection 

 of small chance congenital variations but to definite responses to the 

 environment. In each case, the adoption of a new method of feeding 

 gave rise, slowjy but surely, to a new organisation.^ All subsequent 

 resemblances in the descendants of these ancestral forms are purely 

 convergent. 



Henry M. Bernard. 

 Babington Road, Streatham. 



It seems to me that the striking common structural characters of 

 the classes of animals generally comprised in the Arthropoda oblige 

 us to retain that phylum, at least until phylogenetic speculations 

 regarding its dual origin stand on more certain ground. A primary 

 division of the arthropods into branchiate and tracheate forms seems 

 inadmissible, when we can trace the relationship between the water- 

 breathing king-crab and the mites or harvestmen breathing by means 

 of air-tubes. The morphological and embryological evidence, at 

 present available, appears to point to many-limbed animals with a 

 number of similar segments as the primitive arthropods — the ancestors 

 of crustaceans, arachnids, diplopods, chilopods, and insects. It is 

 likely enough that the stock which gave rise to the three last-named 

 classes had adopted terrestrial life at a very early period. But this 

 stock must have been of a more decidedly arthropodous character 

 than our living Pevipatns, which represents an offshoot at a much 

 lower point in the evolution of the phylum. The superficial 

 resemblance of Peripatns to a myriopod cannot blind us, for instance, to 

 the fact that its antennae are pre-oral, while those of insects and 

 chilopods are primitively post-oral. And Mr. Sedgwick has lately 

 stated his opinion that it stands about half-way between arthropods 

 and annelids. If we recognise its excessively primitive nature, it may 

 be most convenient to retain it in the arthropod phylum, remembering 

 that its tracheae — a necessary adaptation to a terrestrial life — do not 

 require us to regard it as approximate to the immediate ancestors of 

 insects and centipedes. 



Dublin. Geo. H. Carpenter. 



May I point out that, first and foremost I am as little inclined to 

 agree with the view put forward by F. Miiller, and adopted by so 

 many authors, that the nauplius represents the starting point and 

 ancestral form of the Crustacea, as I am to agree with Haeckel's 

 strongly formulated interpretation of the importance of the zoea in 

 the derivation of the Malacostraca. Twenty years ago in my " Unter- 

 suchungen zur Erforschung der Genealogischen Grundlage der 

 Crustaceensystems " I sought to show that the zoea, so extremely 

 variable in form, has no phylogenetic significance, but only represents 

 iSee Nature, vol. 1., p. 546, 1894. 



