44 AMERICAN HYDROIDS. 



these forks arose incipient colonies. After a week had elapsed the parent colony died and the 

 main stem became withered and dropped to the bottom of the jar, carrying with it the daughter 

 colonies, which were then able to attach themselves and proceed with their development as would 

 any other colony. 



After a careful search through the literature of the subject, I am unable to find any account 

 of this mode of reproduction either among hydroids or any other of the metazoa, and I propose 

 for it the name Stoloniferous reproduction on account of the great similarity which it bears to that 

 process among plants. 1 



Asexual multiplication has long been known to exist among the hydroids, where it usually 

 presents itself in some form of gemmation. Fission has been found to occur in a medusa, Stomo- 

 bracltium mirabile Kiilliker, but the most remarkable case heretofore recorded is described by 

 Allman in a campanularian named by him Schizocladium ramoitum.'' The process is, in brief, as 

 follows: 



An ordinary ramulus, instead of bearing a hydranth on its distal e7id, elongates and the 

 crenosarc ruptures the chitinous investment at the tip and protrudes naked into the water. A 

 constriction takes place by which this naked cienosarc is divided off and finally separated from 

 the parent stem. "The detached segment is now the T jj of an inch in length, and strikingly 

 resembles a planula in all points except in the total absence of vibratile cilia. It attaches itself 

 by a mucous excretion from its surface to the walls of the vessel, and exhibits slight and very slug- 

 gish changes of form. After a time a bud springs from its side, and it is from this bud alone that 

 the first hydrauth of the new colony is developed." 



Although this process resembles the Stoloniferous multiplication of Plumularia pinnata in the 

 formation of a new colony from a modified branch termination, it differs greatly in the fact that 

 in Schizoi'ladiitm the divided portion or "frustule," as Allman calls it, becomes entirely separated 

 from the parent stock before the new colony begins to develop, while in P. pinnata there is a vital 

 connection by means of the greatly elongated hydrocladinm. 



The Stoloniferous multiplication must not be confounded with any of the many modes of 

 branching heretofore found among the hydroids, which do not give rise to separate colonies having 

 independent hydrorhi/a?; neither is it equivalent to the multiplication often effected by mutilation. 

 There is no mutilation in this case, unless we may so regard the spontaneous atrophy of the con- 

 nection between the old and the new colonies. 



That this Stoloniferous multiplication is normal is indicated by the fact that specimens fresh 

 from the sea exhibited the greatly elongated and forked hydrocladia. 



It may be well to note that P. pinnata seems to have reproductive powers greater than those 

 of any other plumularian known to me. At the proper season that part of the stem from which 

 the hydrocladia spring is fairly packed with gonangia which may even be crowded out on to the 

 hydrocladia. In some instances it seemed as if the reproductive potentiality demanded some 

 other outlet, and long processes, exactly like the hydrocladial processes described above, were 

 seen springing from the interior of the gouangia themselves. 



THE POSSIBILITY OF CONJUGATION AMONG THE PLUMULARID.E. 3 



During the months of June, July, aud August, 1895, a small species of Aglaophenia was 

 brought almost daily to the Naples Zoological Station. It grows on a long ribbon like alga in 

 shallow water and bears a general resemblance to A. pluma Liuuieus, from which it differs in 

 exhibiting a frequent intercalation of intervening internodes on 'the distal half of the stem, in the 

 more distant hydrocladia, and in having, as a rule, not more than three hydrothecie to each inter- 

 node. 



In June it was noticed that a large proportion of the colonies had the end of the main stem 



1 "Stolons are trailing or reclining branches above ground which strike root where they touch the soil, anil then 

 send up a vigorous shoot which has roots of its own, and becomes an independent plant when the connecting part 

 dies, as it does after awhile." Gray, School and Handbook of Botany, p. 37. 



Reports of the British Association, 1870, and Gymnoblastic Hydroids, pp. 151, 152. 



* The description that follows the heading referred to is from an article by the author in the American Naturalist, 

 November, 1895. Figs. 117-123 are from the same source. 



