PRESERVATION OF THE POLYPIDOMS OF ZOOPHYTES. 241 



face, and towards the upper margin ; it is of a crescentic form, and 

 placed obliquely, as it were, across the upper and internal angle of the 

 cell, with the convexity of the curve directed upwards and inwards. 

 The lips of the aperture are strengthened by thin bands of horny 

 material ; and, under favourable circumstances, indications of short 

 muscular fibres, for the purpose of opening or closing the aperture, may 

 be observed." 



The shell, which Mr. Busk believes to be entire at the bottom, 

 though closed only by a very delicate membrane, contains an ascidioid 

 polyp, of the usual typical form of that class. '* It has ten tentacles, 

 and no gizzard. Two sets of muscular fibres at least may be distin- 

 guished as appertaining to the polyp. The most important of these 

 are the retractor muscles, which, arising from the bottom of the cell, 

 in the form of long, somewhat flattened, transversely striped, isolated 

 fibres, about the one ten-thousandth of an inch in width, are inserted, 

 some of them at the base of the tentacles, and others lower down the 

 body of the polyp." 



When we consider the minuteness of the delicate little sprig which 

 is the natural size of this polyp, we cannot but wonder at the triumphs 

 of the microscope in giving such precise details as Mr. Busk relates of 

 the Notamia bursaria. Its beautiful and perfect organisation, the care- 

 ful provision for the safety and engagements of this minute being, make 

 us awe-stricken at the power of Divine intelligence. 



PRESERVATION OF THE POLYPIDOMS OF ZOOPHYTES. 



The following excellent and simple plan for preserving Zoophytes 

 as wet preparations, so as to retain the polyps and their tentacular arms 

 in situ, was proposed by the late Dr. Golding Bird. " For this pur- 

 pose a lively specimen should be chosen, and then plunged into cold 

 pure water; the polyps are killed almost immediately, and their ten- 

 tacles often do not retract : proper-sized specimens should then be 

 selected, and preserved in weak alcohol. Little phials about two inches 

 long should be procured, made from thin flat glass tubes, so as to be 

 half an inch wide, and about a quarter of an inch, or even less, from 

 back to front. The specimens should be fixed to a thin platinum wire, 

 and then placed in one of these phials (previously filled with weak 

 spirits), so as to reach half-way down. When several are thus arranged, 

 they should be put on a glass cylinder, and removed to the air-pump. 

 On pumping out the air, a copious ebullition of bubbles will take 

 place; and many of the tentacles previously concealed will emerge 



