240 



LEISURE-TIME STUDIES. 



divisions of the animal and plant world, the mere existence 

 of which in the pages of scientific works constitute the veri- 

 table eyesores of the naturalist. This fertility of form and 

 novelty of structure and function in which living nature seems 

 to delight, causes the multiplication of new orders and 

 classes for the reception of those beings which, 

 whilst presenting certain resemblances to well- 

 established groups, nevertheless also exhibit 

 differences of such material kind that the 

 naturalist is compelled to construct for their 

 especial behoof new divisions in which, it may 

 be, only a single abnormal animal or plant 

 may come to be contained. There exists, for 

 example, a singular creature known to naturalists 

 as Sagitta (Fig. 34), which attains a length of 

 about an inch, and presents itself as a clear, 

 transparent little body, bearing a faint resem- 

 blance to an arrow in outward form, this re- 

 semblance giving origin to its scientific name. 

 Sagitta swims on the surface of the ocean, and 

 possesses a hinder fin, representing the feather 

 of the arrow, the head being fringed, as it were, 

 with a series of bristles. Now this curious 

 little animal exemplifies, in an exceedingly in- 

 teresting manner, those difficulties of the natur- 

 alist which arise from the apparent caprice of 

 nature in the production of beings whose 

 nearest relations, as determined by science, 

 are so far removed from them as to necessitate 

 the construction of special divisions of the 

 ;: animal world for their reception. Sagitta was at 



FIG. 34. Sagitta 

 and its struc- 

 ture : a, head ; 

 b, termination 



ductive organs. rst re garded as an abnormal crustacean, and 

 as a distant relative of the crab and lobster class. Then it 

 was regarded as an errant shell-fish, and it has, in the course 

 of its scientific travels, found a temporary home even amongst 

 the vertebrate animals. Ultimately, it has settled down 

 within a division of the animal world specially constructed 



