INTRODUCTION. 1 1 



termed, the rostra, being transparent; near which also is 

 sometimes observed a jjinkish spot simihirto tliat which is seen 

 in the infusory animalcules. The vascular network has now 

 disappeared, and the zoospores lie detached in the cell. At 

 length the granules become perfected, and they are now seen 

 moving restlessly about the interior of the cell, frequently 

 striking against its walls, as though anxious to escape from 

 the confinement of their narrow cell, and to rove about, inde- 

 pendent beings, through the waters, in search of an ap- 

 propriate abiding-place. Having escaped from the cells, 

 Avhich they are enabled to do, not as Agardh supposed, by 

 the multiplied knockings of their beaks against its sides, 

 whereby its fibres become displaced, but either by rupturing 

 its walls, through their increased developement, as in Lyng- 

 bya, Sec, or by some special provision, as in Vesiculifera, 

 Zygnema, &c., they fall into the Avater, through Avhich they 

 speedily begin to move hither and thither ; now progressing 

 in a straight line, with the rostra in advance ; nov/ wheeling- 

 round and pursuing a diiFerent course ; now letting their 

 rostra drop, and oscillating upon them, like (to compare 

 small tilings with great) balloons ere the strings are cut, or 

 like tops, the centripetal force being nearly expended ; now 

 altogether stojiping, and anon resuming their curious and 

 eccentric motions. Truly wonderful is the velocity with 

 which these microscopic objects progress, their relative speed 

 far surpassing that of the fleetest race-horse. After a time, 

 however, which frequently extends to some two or three 

 hours, the motion becomes much retarded, and at length, 

 after faint struggles, entirely ceases, and the zoospores then 

 lie as though dead : not so, nevertheless ; they ha^-e merely lost 

 the poAver of locomotion; the vital principle is still active 

 Avitliin them, and they are seen to expand, to become par- 

 titioned, and, if the species be of an attached kind, each zo- 

 ospore Avill emit from its transparent extremity tAvo or more 

 radicles, whereby it becomes finally and for ever fixed. Strange 

 transition, from the roving life of the animal to the fixed 

 existence of the plant ! In exact correspondence Avith this, 

 is Avhat occurs Avith the Zoophytes. 



