ANTHOMEDUS.E SARSIA. 



55 



develop 4 long tentacles, and are set free in an immature state, but during the last half of 

 the breeding season they fail to develop tentacles or give rise to mere short lashes upon their 

 basal bulbs; and they become sexually mature while attached to the hydroid, the manubrium 

 of each bud being greatly distended with the genital products. This observation was first 

 made by L. Agassiz, 1862 (pp. 189, 203), and has been confirmed by us in hydroid stocks 

 obtained in Swallow's Cave, Nahant, Massachusetts. Plate 3, fig. 5, is derived from one 

 of these sexually mature medusa-buds found upon a hydroid on May 8, 1897. It will be 

 observed that the manubrium of the bud is distended with sperm, while the tentacles are not 

 developed. In this connection it is interesting to observe that Pennaria and Podocoryne 

 carnca sometimes give rise to medusae which are sexually mature at their time of liberation, 

 while in other stocks of the same species the medusae are set free in an immature condition. 

 Garstang, 1894, observes the same phenomenon in the European S. sarsii. 



This hydroid of our Sarsia is very abundant, from March until May, in Massachusetts 

 Bay, where it appears to grow equally well both in pure sea-water and in the brackish mouths 

 of rivers. The medusae appear in great numbers on the southern coast of New England 



FIG. 18. Hydroid and medusa of "Sarsia Jensa," after Hartlaub, in Nordisches Plankton. 



between February and April. They become rare during May, and are not seen during the 

 summer months. The hydroid extends northward to the Greenland coast, but has not been 

 recorded from Beaufort, North Carolina, or farther south. Linko and Birula, 1896, found 

 it in the White Sea, and Linko, 1905, records it from the eastern parts of Barents Sea between 

 Kanin and Kolgujew Islands. Calkins, Torrey, and Hartlaub have found this medusa 

 along the Pacific coast of America as far south as Chile. I believe Syncoryne densa Hartlaub 

 from Helgoland to be an environmental form of S mirabilis. 



We have observed an abnormal medusa of Sarsia mirabilis in which a single well- 

 developed tentacle arose from the side of the manubrium at the point of juncture of the long 

 tubular basal region and the gemmiferous part of the manubrium. (See plate 4, fig. i). This 

 abnormal tentacle was studded with clusters of nematocyst-cells. It lacked a basal bulb 

 and had no ocellus. Asexual budding of medusa- from the walls of the manubrium is not 

 known in Sarsia mirabilis. Medusae of Sarsia with branched manubria are described by 

 Hartlaub, 1896, 1907. 



Professor Hartlaub finds that in Sarsiti mirabilis the stomach is confined to the distal 

 end of the manubrium and the gonad is confined to the mid-region of the manubrium above 

 the stomach. Both the proximal and distal ends of the manubrium lack the gonad. On the 

 other hand, in S. brachygaster and S. cximia there is no differentiated stomach-region, and 

 the gonad may extend over the whole, or nearly the whole, length of the rnanubrium. 



