93 



success ; it seem probable therefore, that they are but 

 sparingly developed. The form of these organs is urn- 

 shaped, with short tubular orifices superiorly, which are 

 placed a little on one side ; inferiorly they contract into short 

 and bent peduncles, which from their calcareous structure 

 must necessarily be very brittle. 



In some of the Sea Mats, the reproduction is also effected 

 by what may be called ovarian vesicles. In the Fliistra 

 membranacea for instance at certain seasons of the year, long 

 membranous sacs are seen protruding from the cells; they 

 are of a yellow colour semi-transparent, and filled with 

 minute yellow granules which appear to be ova. They grow 

 from the side of the cells ; at first they are so small as to 

 cause no apparent inconvenience to the polype; but as it 

 increases in size the polype suffers considerably, and finally 

 dies. The sac then occupies the whole of the cell. It is not 

 in every cell that they are developed, for they are irregularly 

 distributed over the whole polypidom. From the minute and 

 delicate nature of the polypes it is impossible, with our 

 present means, to discover whether their formation depends 

 on any peculiarity in the polype itself, or is the result of 

 accidental causes. From the irregularity of the develope- 

 ment, however, it seems to be governed by no law. Some 

 authorities doubt that this is the true function of the sacs, but 

 from what I have observed I have but little doubt on the 

 subject. 



In Tuhularia and the kindred genera, the gemmules are 

 formed interiorly, and rnay occasionally be seen escaping in 

 the shape of minute ciliated grains, which move about freely 

 from spot to spot, but shortly become fixed rooted anil assume 

 their adult specific forms. This nmde of reproduction, ob- 

 served so extensively among Zoophytes, is among the most 

 curious in nature. In the first place we observe minute grains 

 clothed with cilia whicli are in constant action, and by which 

 they move freely about with all the irregularity of voluntary 

 motion ; in the next they become rooted and grow into 

 various arborescent forms, endowed with unequivocal marks 

 of animal life ; changes which even the wildness of imagi- 

 nation would hardly have conceived. But if we turn to any 

 department of nature, we shall be surprised at the inex- 

 haustable gradations of form and diversity of phenomena; 

 and their almost miraculous termination in results and forms, 

 the very best that could have been devised for the situation 

 each is destined to occupy in the scale of being. However 

 obtuse our intellects may be, these things will force them- 

 selves on our attention ; and to the naturalist, they form 

 one of the chief sources of his pleasures. 



M 



