g LUCE RNARI/E AND THEIR ALLIES. 



morph, direct from the eg-, is a medusoid cephaloid; the hydra-morph is left 

 undeveloped to the lowest degree, in fact totally fails to appear, while the 

 medusoid differentiates to the highest degree. This is just the reverse of what 

 we observe in Clava, Hydractinia, Hydra, etc. Between these two extremes are 

 found all possible intermediate grades in the reciprocally proportionate development 

 of the hydroid to the medusoid ; and singularly enough they are exhibited in 

 Siphonophoraj in an almost infinite variety of morphs, so undecided in form as to 

 leave it sometimes absolutely indeterminable Avhether a certain morph shall be 

 called a hydroid or a medusoid. 



15a. No one holding the present prevailing views in regard to individuality 

 would find a difficulty in seeing that the members of a chain of Salpte are so-called 

 indmd'uals, notwithstanding they are attached obliquely end to end, and orgamcally 

 connected. Now, although in the self-dividing worm, Myrianida for example, the 

 so-called asexual stock may become, by actual separation, two individuals, appa- 

 rently, viz., sexless and sexual, yet once they were more closely connected organi- 

 cally than the Salpte which do not separate. Is now the closer connection of the 

 yet unseparated asexual and sexual parts of the worm to make them less distinct 

 individuals than those of the Salpa I It would seem so, according to the advocates 

 of individualism ; and therefore the Myrianida, with its posterior string of six or 

 seven consecutive sexual buds, is a monocephalic individual. But in the sexless 

 Salpa-form, budding the sexual chain, we have a closer parallelism with the worm 

 than in the chain alone, in fact an identity of relation ; and yet, for all that, we 

 would not think of calling the stock (sexless) and the chain (sexual) together one 

 individual, with one head, but rather many headed, or in other words a 'polymeric 

 unit or individual, of sexual and sexless cephalixms. Therefore, by a parity of 

 reasoning, we ought to denominate the Myrianida and its buds as a succession or 

 series of cejjhalisms. The fact that the worm components are more in one line 

 than in the Salpa only makes an apparently more individualistic body. Among 

 tapeworms the several heads {cephaloids) of the scolex (Coenurus) of Ttenia 

 Ccenurus are not arranged in a line, end to end, but all are free anteriorly, and 

 connected with each other posteriorly by a common body. The closer connection 

 of the subdivisions of the annelid is only one of degree; and as to having more 

 organs in common than the Salpa, it is rather like the community of interest 

 which the coral ceplialisms have in the main trunk. 



156. Since the sexual and sexless are necessary to make up a complete 

 organism, i. e., vegetative and reproductive, the one a complement of the other, 

 neither alone can represent the individual unit, or whole cycle of life: and 

 Cephalism is, therefore, a better term to indicate the potentiality of these sub- 

 divisions to live apart (although this does not always occur, as in corals, Bryozoa, 

 some CampanularicT and Tubularia;), but when living apart (as in other Tubularia; 

 [T. Dumortierii], Laomedea; [Eucope diaphana, etc.], and Salpa?, Myrianida, etc.), 

 meaning more or less incomplete individuals (pseudo-individuals) which are either 

 mainly vegetative or" mainly reproductive, as the case may be. We look upon 

 cephalism, then, on one hand as having a controlling influence of a low degree of 

 independence when shared in common by the multiple heads of a coral polypidom, 



