38, BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



sub-umbrella wall near the bases of its tentacles, and thus the process of form- 

 ing new meduste is repeated in the next generation. The medusae are very- 

 hardy when detached and grow rapidly, and proceed at once to develop new 

 medusae from their own tentacle bulbs. When detached, the bell of the new 

 medusa is about 1.5 mm. in diameter. It is difficult to comprehend the phi- 

 logenetic history of this curious and fortuitous combination of local growth, 

 fusion, and budding which results finally in the formation of a medusa exactly 

 resembling the adult. It is probable, however, that it has been derived from 

 the usual budding process so common in hydromedusge, but that in this case a 

 greater and greater number of parts have been taken directly from the adult 

 medusa, until the present state has been arrived at. After the original tenta- 

 cles have been cast off, new ones grow out in their places, and thus the old 

 medusa always has 12 tentacles. After every one of the original 12 tentacles 

 has been cast off, however, the process of forming new medusa; becomes less 

 active and finally ceases altogether. Then the gonads develop in 4 separate 

 interradial regions on the wall of the gastric part of the proboscis. In the 

 female the ova become very prominent, and are finally dehisced into the water. 

 I was unable to raise them, however, and know nothing of the development of 

 the sexual generation. The proboscis is flask-shaped, and there are 4 simple 

 cruciform lips. The entoderm of the proboscis tentacle bulbs and circular 

 canal is ochre-yellow, all other parts of the medusa being transparent. The 

 medusa is very active and thrives well in confinement. Large numbers of 

 them appeared at the Tortugas, Florida, on May 21, and continued more or less 

 common until June 4, 1899. 



TURRITOPSIS, McCradt, 1857. 

 Turritopsis nutricula, McCbadt. 



Turritopsis nutricula, McCrady, J., 1857, Gymn. Charleston Harbor, p. 25, Pis. 



IV., v., VIII. Fig. 1. 

 Modeeria multitentacula, Fewkes, J. W., 1881, Bull. Mus. Comp. Zool. Harvard 



Coll., Vol. VIII. p. 149, PI. III. Figs. 7-9. 



This medusa was well described by McCrady in 1856 and 1857. Fewkes, 

 1881, however, redescribed it as a new species under the name " Modeeria 

 multitentacula." To add to the confusion respecting this species, a medusa 

 that has since been identified by Martha Bunting, 1894, as Podocoryne carnea, 

 was described by A. Agassiz, 1862, 1865, under the name of " Turritopsis 

 nutricula." The latter author was deceived by the close resemblance of the 

 young of Podocoryne carnea to the young medusa of T. nutricula, McCrady, 

 1857, into the belief that the two were identical. The mature medusa;, how- 

 ever, are easily distinguished one from the other, and the hydroid stocks differ 

 widely from each other. 



