116 ACALEniS IN GENERAL. Part I. 



stands in (lii-ect communication with a special stem of the chjmiferous s3-stcm, 

 occupying a central position in the axis of the hody, while in DiscophoriB there 

 is one eye to each simple radiating tuhe. 



Thus, whatever be the special condjination of the organs in the Disco])hora? 

 proper, and however high they may appear to stand on account of the extra- 

 ordinary development of some of their parts, the sum total of the structural 

 complication in the Ctenophora> is unquestionably greater than that of the Dis- 

 C02)hora\ This will appear more distinctly', when we consider the similarity in 

 general appearance of the Discojdiora to the naked-eyed Medusa? born from 

 Hydroids. In this connection it must also be remembered, that, wdiile the majority 

 of Discophora; enjoy only a consecutive individuality (see p. 97), since several 

 Medusa? arise from the division of one single larva, in Ctenophoraj the reproduction 

 takes place by a direct metamorphosis, each egg producing a single individual. 



If multiplication of identical parts is everywhere an indication of inferiority, and 

 definite numbers with definite relations a mark of superiority, Ctenophorie will 

 undoubtedly take the lead in that respect also over the Discophora^, in which 

 repetition of identical parts prevails, without a perceptible difference in their 

 relations ; while in Ctenophora> the number of spherosomes never varies, and there 

 exist between them such definite relations as simulate bilateral symmetry. 



The Hydroids, as a whole, and considered within the limits assigned to that 

 order in the preceding section, unquestionably occupy the lowest place in the class. 

 For, in addition to the permanent character of indefinite repetition of identical 

 parts, we oljserve among them, almost universally, a more or less characteristic 

 polymoi-phism, sometimes to such an extent that it becomes difficult to distinguish 

 secondary individuals from actual organs. Individuality is almost lost in the 

 dependence in which the mendjcrs of a community stand toward each other. 

 Even when individuality becomes most prominent, it is so in individuals which 

 are short-lived, in comparison to the duration of the combined individuals to which 

 they owe their existence. 



That the Discojjhora? proper constitute a distinct order by themselves, appears 

 plainly from the higher complication of their structure when compared to that of 

 the nakcd-eycd Medusa?. In the latter, the radiating chymiferous tubes are all 

 alike, ecpially distant one from another, simple, and either few or very numerous, 

 and meet with a simple circular tube, instead of forming a complicated network 

 of anastoiuoses along the margin of the disk, as in the Discophora? proper, whose 

 radiating tubes are alternately more or less complicated in their course, some 

 extending as straight tuljes to the margin of the disk and communicathig with 

 the base of the eyes, while others branch in various ways, and end in a net- 

 work of anastomoses at the margin. In Discophora proper, there exist always 



