ZOOPHYTES. 255 



bers of such corpuscula continued to be discharged for above a week. Two 

 of these escaping previous to July 17, were then adhering to the watch- 

 glass, and in an early stage of metamorphosis, fig. 11. 



As the metamorphosis and supervening increment are perfected and 

 advancing respectively, the form of the nascent hydra is clearly exposed 

 through the transparent integument. The body is then seen to be attached 

 by a number of ligaments to the bottom of the cell, and the pencil of the 

 tentacula approaching the summit, where the parts shall relax to allow dis- 

 play of the whole by protrusion on maturity. Descent of the intestinal canal 

 from the stomach, and its return upwards in conformity with ascidian or- 

 ganization, are very distinct, fig. 12. Here is a yellow substance resem- 

 bling an ovum at the bottom. 



All the cells of this zoophyte are originally separate as those of the 

 Sertularia arcta. 



When the corpuscular gemmules come to afiix themselves to some 

 slender substance, and there undergo their metamorphosis, the bases of 

 the generating cells are opposed to each other. 



Neither of these two species has been of frequent occurrence in Scot- 

 land, but skilful naturalists seem to have found abundance elsewhere. 



Plate LIII. Fig. 1. BowerhanJcia repens 



2. The same enlarged. 



3. Portion magnified. 



4. BowerhanJcia densa. 



5. Another specimen. 



6. Upper portion of fig. 4 enlarged. 



7. Section of fig. 5. 



8. Hydra. 



9. Corpusculum or gemmule. 



10. Group of corpuscula. 



11. Corpuscula metamorphosing. 



12. Nascent hydra from a corpusculum. 



All the figures of this plate, except figs. 1, 4, .5, are enhirged. 



Whatever new names, whether original, modified, or altered, are found 

 in this volume, they must be regarded as mere temporary and provisional 

 substitutes, liable to such correction as expedient. 



