Chap. I. SUB-ORDERS OF CTENOPIIORiE. 185 



prove the tA-pe of a distinct 8ul>-order, these Cteiiophorai may be called Tankdcc. 

 A few Acalephs referred to the order of Cteiiophora^ do not belong to it at all ; 

 such are the Beroe Gargantua Less., which is a genuine Discophore, and the Acils 

 Less., which are mostly Siphonophora?. Berosoma Less, may be a Pyrosoma ; but 

 since it was described and figured from memory, it hardly deserves further notice 

 till it has been observed satisfactoril}''. 



It may now be asked how far these sub-orders may be superior or inferior 

 to one another. This is a question which I am not fully prepared to answer. 

 Indeed, it seems as if natural sub-orders exhibit fewer indications of superiority 

 or inferiority among themselves than any other kind of natural divisions in the 

 animal kingdom, the characteristic features of sul>orders resting chiefly upon the 

 prominence of one or the other subordinate elements of the structural complication 

 which distinguishes the order itself We find, for instance, that while the inter- 

 amlndacral chjnniferous tube is wanting in the Eurystoma\ they have a large oral 

 tube, which is wanting in the Saccataj ; but these have a complicated tentacular 

 apparatus with a double interambulacral tid^e, all of which is wanting in the Eu- 

 rystoma3 : and again, the Loljata) have four auricles and two lobes of the sphero- 

 some, which do not exist in either the Saccatoj or the Eurystoma?, but in the 

 Lobatfe the oral tube is small and the tentacular apparatus very imperfect in 

 comparison to that of the 8accata2. So that, unless compai'ative endjryology 

 some day furnishes the means of determining the relative importance of these 

 structural difterences, it is not likely that these sub-orders can be linked together in 

 a gradual series, without fiilling back upon arbitrary considerations for their sys- 

 tematic arrangement. 



McCrady, who has admitted as 8ul)-orders the same divisions which Leuckart 

 calls orders, does not hesitate to consider the Bcroids proper as superior to the 

 tentaculated Ctenophora^. It seems to me that his argument is untenable. The 

 reduction in the number of identical parts is truly a character of superiority, and 

 the absence of tentacles in the Ctenophoraj Eurystoma* might be an indication of 

 their superiority, if the tentacles of Ctenophorte were homologous with the teirtacles 

 of Discophorte ; but I have proved that they are not, their position showing 

 distinctly that they are an interambulacral, and not an amludacral, apparatus. 

 Their limited number in some Ctenophora^, and their total alosence in others, are 

 therefore not to the point. I am rather inclined to assign to the Beroids jaroper 

 the lowest position, on account of that very aljsenee of tentacular apparatus, the 

 presence of which in Saccataj and Lobata3 I view as an additional structural 

 complication ; and, judging from Mr. McCrady's own statements respecting the 

 embryology of Bolina, which I have not myself traced, I would assign the highest 

 position to the Lobatoe, on account of their resemblance to the Saccata) during 



VOL. HI. 2i 



