18 " ENDEAVOUR " SCIENTIFIC RESULTS. 



Somewhat larger forms differ in the greater prevalence of 

 internodes of the second, third, and higher orders ; and with the 

 longer internodes is associated a much less divergent condition 

 of the hydrothecSB borne by them, though in the distal portions, 

 where only a single pair occupies an internode, they may differ little 

 or not at all from those of the smaller form. The stem-internodes, 

 or many of them, are long, supporting two pinnae and six 

 bydrothecae, and are especially characteristic of the species. In 

 the smallest variety the stem-internodes are arranged in the 

 typical Sertularian fashion, that is to say each internode bears 

 at its base a pinna with its axillary hydrotheca, and above it a 

 pair of hydrothecae, usually sub-alternate. In the larger forms 

 we find that a stem-internode generally has on one side a pinna 

 with three hydrotheca? above it, and on the other a hydrotheca 

 near the base, then a pinna, and above the pinna two hydrothecae. 

 This arrangement was mentioned by Busk (from whom I received 

 a drawing of it), and by later observers, and naturally appeared 

 somewhat bizarre to those who did not notice that the long 

 internodes were simply equivalent to two of the shorter ones 

 united. The nodes are oblique, sloping alternately to right and 

 left when the internodes are single, but in a series of the double 

 internodes, evei'y alternate node being suppressed, the nodes all 

 slope in the same direction. It is not implied that the double 

 internodes are formed from two originally single ones by the 

 obliteration of the dividing node, as often occurs in Sertularella 

 and elsewhere ; they are, I have no doubt, formed continuously 

 in the first instance. In the smallest forms single stem-internodes 

 are the rule, aud often occur exclusively ; some of the larger 

 varieties have only the double type, others have single and 

 double ones interspersed without definite order, or more commonly 

 double ones at the base and middle, and single ones near the 

 summit. 



Among other varieties we find some in which the pinna- 

 internodes are still longer, and single-paired internodes are few or 

 entirely wanting ; even the distal hydrotheca? may be much less 

 divergent, and a ti*ausition to the genus Tluiiaria is shown by 

 the hydrotheca? on the proximal portions of the pinnae, which are 

 often neither opposite nor distinctly paired, but may vary from 

 opposite to alternate, while they are sepai'ated in front, One 

 pinna may have internodes with sixteen or eighteen pairs, all 

 opposite or neai'ly so, while another on the same stem may have 

 them almost exactly alternate. Another specimen has pinna' 

 consisting of a single internode, and bearing over twenty pairs of 

 hydrothecae, all strictly opposite, in contact in front, and with 

 only the mouth portion divergent, in short, not distinguishable 

 from a Thuiaria, 



The larger specimens collected by the " Endeavour " differ 

 from other varieties in their attenuated condition. The stem- 



