ESCHARID.E. 329 



perforated on the top. Ovaria rather small, globose, rough, and 

 shining with a pearly lustre ; the aperture lateral and circular. 



This is more calcareous in its texture than the preceding, and 

 hence assumes a white colour when dried. When perfect and young 

 there are two short spinous teeth on the sides of the cell inclined in- 

 wards, but in old or exposed specimens no vestige of them can be 

 discovered. In the same specimen a considerable difference in the 

 shape of the aperture of different cells often exists, from a wide and 

 perfect oval to a short angular form, and on each side of the former 

 we may commonly detect a small auricle or perforation. Many of 

 the cells, too, are sometimes furnished with a broad reflected calcare- 

 ous lip to the lower side of the aperture. 



"Animal hydra pellucida hyalina, corpore cylindrico, in extensione 

 cellulis duplo longiore, tentaculisque duodecim in formam infundi- 

 buli extensis terminato. 



" Vix ultra octo dies vivunt haec animalcula, sed progenie numer- 

 osa brevi tempore ad marginem augentur prolifera, dum centre pro- 

 priora moriuntur. Prreterea ovulis deciduis multiplicantur et in 

 hoc ut in cseteris cum Brachione tubifice 111. Pallas mores similes 

 habet. 



" Ovaria ut in Sertulariis plurimis nunquam vidi nee in hoc nee 

 in aliis flustrarum speciebus, sed more hydrarum ovula excernunt." 

 Midler. 



FAMILY ESCHARID.E. 



Several species in this family are distinguished by the possession 

 of certain singular moveable organs which have been compared to a 

 bird's head in miniature, and which are attached to the sides of the 

 cells. Mr. Charles Darwin has made some interesting observations 

 on them in species collected on the shores of Terra del Fuego and of 

 the Falkland Islands, which I shall copy in this place, for I have 

 verified their exactness in our native species. He says, "The organ, 

 in the greater number of cases, very closely resembles the head of a 

 vulture ; but the lower mandible can be opened much wider, so as 

 to form even a straight line with the upper. The head itself posses- 

 ses considerable powers of movement, by means of a short neck. In 

 one zoophyte the head itself was fixed, but the lower jaw free ; in 

 another it was replaced by a triangular hood, with a beautifully- 

 fitted trap-door, which evidently answered to the lower mandible. 

 A species of stony eschara had a structure somewhat similar. In 



