LUCERNARI.E AND THEIR ALLIES. 



of two rows, or perhaps three ; the true rows lie so close together that the slightest 

 possible swerving of the tips of the tentacles to one side brings those of neigliboring 

 ranks so nearly into line that the eye fails to detect the want of perfect continuity 

 in it. It must be kept in mind here, though, that the globose tips of these organs 

 stand at a considerable distance apart, and that their range is over a long line which 

 is arched in tlie direction of the plane in which the file trends (cut 2). The eye, 



Cut 3. 



therefore, cannot take in the whole file of tips at once, but must pass from point to 

 point, and in so doing the slight divergence from the plane is not noticed. Still 

 it is possible to determine to a certainty whether a file is single, or double, or triple, 

 or more; but we must confess that it was not until after we had become familiar 

 with these bodies and their various attitudes, by long and painstaking observation, 

 that we could come to any definite conclusion, even as to their general arrangement, 

 much less in regard to their special taxis. 



92. The clue to the one-sidedness of a group was not detected until the process 

 of development had been traced in young animals. It is true that by following 

 ?iuy one tentacle of a file down to its base, where it Avas in contact Avith others all 

 around it, we could determine whether it originated from the same line as the others 

 next to it in the apparently single row above ; but the large number of the group 

 taken together, and the crowded state of the numerous younger tentacles was a 

 great hindrance to a true appreciation of their relations. The clue once dis- 

 covered, though, in the young animal, it was no difficult matter to see the trend 

 of the development of these organs, and a reason for the asymmetry of a bunch in 

 the adult ; but still, such were the obstacles arising from numbers, approximate 

 identity m size, the convex surface over which they were spread, and in particular 

 the mobility and unstable condition of this surf\ice in the region Avhere the younger 

 tentacles were budding and growing, that it was impossible to determine the exact 

 status of each one, either in regard to dimensions or relative position. This has 

 been accomplished with the fullest satisfaction in the young. (^ 149, 150, 155); 

 showing, incontestably, that the older tentacles preponderate on that side of a group 

 which lies next a partition, but the investigation was not carried on far enough to 

 torm a groundwork for the deduction of a mathematical formula of taxis, although 

 It seemed quite probable that it was a rather high figure. Our diagram of the 

 taxis (cut 4) of a group of an adult animal, must be taken, therefore, only as 

 approximate and general. The value of the diagrams of development in tlie 



