304 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 37. 



CATABLEMA VESICARIA (A. Agassiz). 



Plate 30, figs. 3, 4; plate 31, fig. 6. 



Turris vesicaria A. Agassiz, '62a, p. 97. 

 Catablema vesicaria JiAECKEL, '79, p. 64. 



This interesting boreal species is represented in the collection by 

 27 specimens in various stages of development. The adult has been 

 so well described and figured by A. Agassiz ('65), by Haeckel ('79 

 " C. campanula") and by Maas (:04) that no extended account is nec- 

 essary here. However, young stages have not previously been de- 

 scribed, so far as I am aware. 



In general form the series agrees closely with the figures of A. 

 Agassiz and of Maas, an extreme development of the apical gelatinous 

 projection (pi. 30, figs. 3, 4) being an important characteristic of the 

 species. 



Tentacles. — The largest specimen (19 mm. high by 17 mm. in diam- 

 eter), which is in about the stage figured b}^ A. Agassiz ('65, fig. 262), 

 has twenty-two well-developed tentacles and twenty rudimentary 

 tentacular knobs rather irregularly distributed. In another speci- 

 men of nearly as great size (18 by 14.5 mm.) the development of the 

 tentacles has progressed somewhat further, there being thirty-seven 

 large and only two rudimentary tentacles. According to Haeckel 

 from thirty-six to forty-eight tentacles are finally formed. The 

 smallest specmien, 3 mm. high by 3 mm. in diameter, has four large 

 radial tentacles, four somewhat smaller interradial tentacles, and 

 eight minute adradial tentacular knobs. This condition indicates 

 that the order of development of tentacles is successively radial, in- 

 terradial, adradial. In normal development subradial rudiments next 

 appear. But in all the present specimens the development of addi- 

 tional tentacles, after the first three series, is irregular, no two quad- 

 rants of any specimen being precisely alike. Thus in an individual 

 10 mm. high by 9 mm. in diameter, in which the first traces of gonads 

 are visible, inter- and adradial tentacles have alone appeared in one 

 quadrant, while in all the other quadrants subradial rudiments are 

 also present. In still later stages the development of additional ten- 

 tacles is so irregular that the normal succession is entirely masked. 



The tentacular bases are laterally compressed and bear spurs clasp- 

 ing the exumbrella (pi. 31, fig. 6, T. Ra.). It is not unlikely that their 

 outline, which appears constant, will prove to be of specific signifi- 

 cance. Ocelli are recorded for this species by A. Agassiz ('65), and 

 can be determined on a few specimens in the present series. In most 

 cases, however, none are distinguishable. In all probability they have 

 disappeared as the result of preservation, since neither Haeckel (79) 

 nor Maas (:04) observed any such organs in the preserved specimens 

 which they examined. 



