570 <^'has. W. Hargitt 



more disk-slmi)cd, teutaeles bud froin the margius of the disk, and 

 continue to grow in length, the embryo becomes entirely free in 

 the cavity of the gonophore and later escapes as a typical actinula. 

 differing in no essential respects from those of other well known 

 species of Tìihidaria. 



The actinula is not ciliated and has therefore no special organs 

 of locomotion. On escape it is wholly at the mercy of the waves, 

 or currents for distribution. In the aquarium it usually sinks close 

 by the parent colony, often indeed falliug among them, and seems 

 to fix itself promptly upon anv object with which it comes in con- 

 tact, even the stems of parent hydroids. A careful inspection of 

 colonies of hydroids which were discharging actiuulae in the aqua- 

 rium revealed the presence of young polyps in various stages of 

 growth, from those appareatly but recently attached, to specimens 

 of cousiderable size, and of such maturity that gonophore buds were 

 beginning to develop. It was not unusual to find several of these 

 attached to a single stem, as shown in figure 24 (PI. 22j. As will 

 be noted these young polyps show a definitely annulated perisarc 

 over the entire leugth of the stem, whereas in the adult condition 

 the perisarc is wholly devoid of this feature. 



These observations recalled others of a similar character made 

 upon Conimorplia jiendula , a brief account of which I have else- 

 where recorded^. There were in these eases conditions which seemed 

 to indicate the probabilìty that the small polyps attached to the 

 bases of the hydroid might be independent organisms, and if so 

 perhaps a new species, and they were provisionally so designated, 

 under the name of T. imrasiUca, as indicative of their presumed 

 relation to the larger organism. It is unnecessary to go over in 

 detail the grounds which seemed to justify this conclusion. Suffice 

 it to say that the total aunulation of the perisarc of the small po- 

 lyps, the deeply insinuated rhizoidal attachment, and the presence 

 of gouads were among the more obvious and apparently distinctive 

 characters, which seemed to point toward their specific independence. 



The observations above recorded concerning the history of the 

 })olyp of T. mesembryantkemum^ and also a brief note by Torrt^ 

 concerning similar observations on the young of Conimorpha jjalma 

 incline me to reconsider my earlier views concerning the case of 



1 Amer. Natural. Vol. 36 1902 pag. 549. 



- Hydroids of Pacific Coast. iu: Pubi. Univ. California Z. Vol. 1 1902 pag. :38. 



