157 Geology and Natural History. 



From this summaiy it will be seen that not one of the characters 

 given to worms is, properly speaking, characteristic, or diagnostic, 

 of the Vermes, as a whole, and few of them can be applied to 

 more than a single order, while many of them are common to the 

 worms and various other invertebrates, belonging to diverse 

 classes and branches, including MoUusca. The same remarks 

 apply to most of the additional characters given to Vermes, on pp. 

 58, 59. Some of the latter are even more useless, as distinctive of 

 Vermes. Thus they are said to have " an extensive vascular sys- 

 tem, containing a colored fluid representing the pseudo-htemal 

 system." This has not usually been given as a character for all 

 Vermes," but merely for the higher Annelids ; but it does not hold 

 good even within those limits, for there are many Ohajtopod 

 Annelids, belonging to several diiFerent families, that are totally 

 destitute of pseudo-hsemal vessels, but have only one fluid, which 

 fills the perivisceral cavity, [Ajj/debhta, Polycirrux, Glycera, etc.), 

 and yet some of these genera belong to families in which other 

 genera have a complete system of vessels, (see also JMorse's quota- 

 tion from Claperede, p. 25). The possession of " chitinous out- 

 growths, either as scales, plates, hairs, or spines " is a character 

 that applies only to a part of the true Annelids, most leeches and 

 many Sipunculoids, as well as most of the Helminths (except in 

 the embyos of some) being destitute of such appendages. In fact 

 most of these characters are no more characteristic of worms, as a 

 group, than the presence of a shell is characteristic of MoUusca. 



These facts are brought forward, not for the purpose of refuting 

 Prof. Morse's views concerning the position of Brachiopoda, 

 which, if established at all, must rest on other and better founda- 

 tions, but to show how vague are his definitions of "Vermes," and 

 how indefinite his ideas as to what a loorm really is. The difticulty 

 of defining the heterogeneous group of " Vermes" would be greatly 

 increased by adding to it the Brachiopods and Polyzoa, as the 

 author proposes. Nor can he better the matter, by separating 

 the " Vermes " from the rest of the Articulata, and calling the 

 group a " sub-kingdom," as some other writers have alreany 

 done. In fact, there is far greater diflerence between the Annelids 

 and lower worms (Helminths), than between the Annelids and 

 Crustacea. These two last classes approximate so closely in 

 structure, in some of their forms, that it has become a matter of 

 extreme difticulty to find diagnostic characters for separating 

 them, and few greater absurdities have been proposed in classifica- 

 tion, in modern times, than to separate them in two " sub-king- 

 doms " or branches. On the same basis every class of animals 

 might be made a " sub-kingdom." 



Another feature of the arguments presented demands attention 

 from those who may wish to form an impartial judgment of them. 

 The author naturally takes great pains in every case to point out 

 all the resemblances between the organs of worms and those of 

 Brachiopods that he compares, but he does not always allude to 

 the differences. Thus, on p. 11, he compares the elongated 



