THE PLUMULARID^E. 27 



the case in older specimens, and the sarcostyles were exceedingly active, stretching- across from 

 one leaf to the next, to which they became attached by their adhesive ends and remained in that 

 position for a considerable time (fig. 90). 



It appeared as if these Barcostyles served as a temporary attachment to hold the edges of the leaves together, 

 while the edges themselves were connected by trabeeuhe of cu-nosarc, which rapidly formed a stronger and perma- 

 nent connection. The perisarc of the edges of the leaves seemed exceedingly thin and in places appeared to be 

 wanting. A contact having been established between the edges of the adjacent leaves the permanent attachment 

 was soon formed, and the cmlornic cavities of the leaves established connections at these points. A little later 

 currents of water bearing grannies were seen to How in active streams from one leaf to the other. ' 



After this connection was strongly effected the sarcostyles retracted suddenly within their 

 uematophores. The design of the arrangement and the function of the sarcostyles seemed so 

 evident that I have little doubt that we here have a hitherto unnoted use for these sarcostyles. 



In a study of the mesial sarcostyle of Aglaoplienia species at Naples, I witnessed an apparently 

 conclusive proof that the structure possesses an axial cavity corresponding to the body cavity of 

 the hydranth. 2 When examining a living sarcostyle under a one-twelfth oil immersion lens I could 

 distinctly see the so-called endodermal axis, which was sharply divided off from the ectoderm by 

 the stutzlamelle. The axial endodermal cells were not distinctly outlined in the live specimen. 

 While trying to distinguish these cells I saw, much to rny astonishment, a granular amu'boid cell 

 quickly pass along the exact axis of the uematophore. This cell had very much the appearance 

 of an aimeba, with the exception of the fact that the granules were much more numerous and 

 sharply outlined. The cell was constantly changing form and putting forth pseudopodia with as 

 great rapidity as the most active amoeba (fig. 91). My attention having once been attracted to 

 these strange cells, there was no difficulty in seeing that they were in nearly every sarcostyle 

 examined. Sometimes several were found together in the same sarcostyle. They appeared to be 

 engaged in traveling back and forth along the axial line of the sarcostyle, and none were observed 

 to pass to the ectoderm nor to the cavity of the hydrocladium. Their progress was too rapid and 

 uninterrupted to admit of its being explained as a mere working of a passage between the loose 

 aggregation of eudodernial cells, and the conviction was strong that they were traversing an 

 axial cavity of the sarcostyle. It appeared as if the walls of the cavity were ordinarily in contact 

 but not adherent: as if it were, in effect, a collapsed tube (fig. 89). When the amieboid cells were 

 passing along the very thin walls of the tube could be seen to be parted immediately above and 

 below the cells. The cavity could not be seen in stained preparations, although a careful search 

 was made for it. This maybe due to the fact that the thin walls are collapsed at all times except 

 when forced apart by the passage of the cells. These latter reminded one very strongly of the 

 leucocytes in the human blood. They were afterwards found in abundance in the endoderm of the 

 hydranths and more sparingly in the endoderm of the stem. They were most abundant of all in 

 the rapidly growing terminations of the stems in an undescribed species of AglaopheniaS 



In these positions, however, they were not seen to move definitely from place to place, although 

 the sending forth of pseudopodia was frequently observed. 



As before stated, Semper, who, it seems, was the first to figure the sarcostyles, represented 

 them as having a distinct body cavity. No author has heretofore confirmed this idea, and indeed 

 they seem conclusively proved to be solid when stained and cleared specimens are examined. But 

 the living sarcostyles tell a different story, at least in Antennularia janlni (fig. 92), where it 

 evidently has a narrow axial tube. In this latter species the eudoderui of the sarcostyles was, in 

 some cases, packed with unicellular alga', as was that of Aglaoplienia pinnatu. In some cases 

 these alg:i> appeared to be in an axial cavity, where the thin walls of the tube could be seen 

 parting immediately above and below them, as in the case of the anueboid cells. 



The nematocysts in the sarcostyles of the Eleutheroplea are not numerous, nor do they 

 present any striking features whereby they can be distinguished from those in other parts of the 



C. (_'. Nutting, Notes on Plymouth Hydroids, Journal, Marine I'.iological Association. New Ser., IV, No. 2, 

 February. 1896, p. 153; reprinted in Natural History Bulletin, State University of Iowa, IV, No. 1. May, 1896. 



-This discovery was announced in a paper entitled The Sarcostyles of the Plmunlarida>, read before Section 

 F of the American Association for the Advancement of Science at the Detroit meeting and afterward printed in 

 the American Naturalist. April, 1XH8, p. 223. 



'Tins species is the one mentioned by me in Notes on the Reproduction of Plumiilariau Hydroids, American 

 Naturalist, November, lSfl">, p. 969. 



