BIGELOW: THE "GRAMPUS" IN THE GULF STREAM. 



207 



stages iu the development of the canal system and tentacles.- The number of 

 radial canals in each of the specimens is 4, but the number and degree of develop- 

 ment of the blind centripetal canals, such an important feature iu this genus, 

 varies, not only iu different individuals but in the different quadrants of any one 

 individual. The most rudimentary condition in any quadrant is one in which 

 there are three blind canals, one interradial and two adradial, the interradial, 

 which is the furthest developed, reaching nearly to the base of the manubrium 

 (Fig. 1). Connected with each canal is a well-developed tentacle, as is shown in 

 the photograph, and between the interradial and one of the adradial tentacles is 

 an extremely rudimentary tentacle as yet unconnected with a canal (Fig. 3). 

 From this, as well as from similar instances, it is evident that in the development 

 of additional tentacles and blind canals, the tentacle is formed first, its correspond- 

 ing canal appearing later. In all quadrants the largest blind canal is the inter- 

 radial, a fact showing that it is formed next after the radial canals. After the 

 formation of these three series, radial, interradial, and adradial, further develop- 

 ment of canals and tentacles is somewhat irregular. The numbers of canals and 

 tentacles per quadrant, together with the dimensions of the bell, are given for five 

 specimens in the subjoined table. 



One abnormality was observed in which there are two blind canals in connec- 

 tion with a single tentacle (Fig. 7). The greatest number of tentacles in any 

 quadrant is six ; though in this quadrant only three canals are present. The 

 greatest number of blind and radial canals and of tentacles in any individual is 

 twenty-one and twenty-five, respectively, in the largest specimen. None of the 

 canals unite with the manubrium in any specimen, nor are any of them branched. 

 The blind terminations of the canals are ordinarily simply rounded (Fig. 4) ; in 

 several instances, however, they are variously lobed and dentate (Fig. 2), and it 

 is possible that such a conformation foreshadows a future union with the 

 cruciform base of the manubrium. In the condition of its tentacles and cen- 

 tripetal canals S. nauarchus closely resembles half grown specimens of S. simulans, 

 except that in the former the number of these organs is slightly greater than in 



