HYDROIDA. BALE. 



57 



examining specimens collected by the ' Endeavour " in the 

 Great Australian Bight, that this sarcostyle is not always naked, 

 as described by Ritchie, but is, sometimes at least, protected by a 

 sarcotheca of the most rudimentary form. 



The hydrophyton, in the young state, is monosiphonic, but 

 afterwards becomes fascicled in the older portions. The branches, 

 which are not in any regular order, spring from the internodes 

 of the stem or older branches, not taking the place of a 

 hydrocladium, but originating opposite one. There is much 

 irregularity in the arrangement of the first few iuternodes of a 

 branch. Following the stem-process which supports the branch, 

 there is frequently but one very short internode bearing a 

 sarcotheca only, before the hydrocladia-bearing iuternodes 

 commence; in other cases the first iuternode is much longer, 

 with two or three median sarcotheca?, and sometimes a 

 hydrocladium also. The process itself has usually two sarcotheca?, 

 both on a level and widely apart ; sometimes only one is present 

 however, and in Ritchie's specimens there were three. 



The hydrocladiate tube is mostly composed of single or double 

 internodes, supporting respectively one or two of the alternate 

 hydrocladia, In some specimens the shorter internodes pre- 

 dominate, in others the longer, and frequently the two forms are 

 interspersed at random, while in other cases all the internodes 

 may be alike. T have observed instances in which the first two 

 or three hydrocladiate interuodes of a branch are more elongated 

 still, supporting each three hydrocladia. 



The hydrocladia are at an angle of 45 or somewhat less, and 

 are directed somewhat forward. Their internodes have the 

 perisarc, at the distal extremity, produced a little forward so as 

 to form a thin, delicate, collar-like extension, surrounding the 

 node, and continued into two narrow webs which run backward 

 along the upper side of the internode, to join the sides of the 

 hydrotheca, Midway between these, and under the back of the 

 hydrotheca, is situated the sarcopore. This orifice is obvious 

 enough in a front view of the hydrocladium, but owing to the 

 back of the hydrotheca being immediately above it, it appears 

 closed in, and resembles a circular thin area, for which I mistook 

 it until Ritchie called attention to its true nature. On one of 

 the "Endeavour'' specimens, which, when cleaned with liquor 

 potassa? and mounted in glycerine, was absolutel}- colourless and 

 of glassy transparency, I was able not only to verify Ritchie's 

 observation, but to discover a distinct sarcotheca (if the term 

 may be applied to a structure so rudimentary), just over the 

 orifice. As seen in front view it is simply a tongue-shaped flap 

 of the perisarc, of excessive delicacy and tenuity, visible through 

 the back of the hydrotheca, and usually projecting slightly 



