Miscellaneous. 209 



good deal of attention. The specimens upon which these observa- 

 tions were made, were found by Mrs. Macdonald on the 15th of Sep- 

 tember last, adhering to the lower surface of a stone lying in a shal- 

 low pool near low- water mark. When obtained, they were between 

 thirty and forty in number ; and the largest was between two and 

 three lines in length. When examined under the microscope, they 

 presented characters somewhat intermediate between a hydraform 

 and actiniform polype, but still different from either ; and it was not 

 until Dr. Reid had completed his examination of their structure, 

 that he discovered that this animal had been described by Sars, first 

 under the name of Scyphistoma, and afterwards as the young of one 

 of cur common Medusae (Medusa aurita). 



After giving a description of the external characters of these ani- 

 mals, and pointing out that this agreed in the main with that by 

 Sars, Dr. Reid then proceeded to explain the results of a more mi- 

 nute examination of their structure. 



The body of the animal is composed of two distinct layers — an in- 

 ternal and an external. The internal contains numerous nuclei and 

 nucleated cells, is thicker and more opake than the external, which, 

 on the other hand, is chiefly composed of a structureless substance, 

 having numerous oval cells (filiferous capsules) on its outer surface, 

 measuring about 2-oVo tn P art °f an i ncn m tne i r largest diameter, and 

 having coiled up in their interior a long spiral thread, which was 

 occasionally seen uncoiled, and projecting from one end of the cell, 

 along with its lining membrane. Filiferous capsules are also found 

 in smaller number upon the inner surface of the internal layer. The 

 internal layer, which, as has been already stated, is so rich in nuclei 

 and nucleated cells, is folded inwards, and forms the four projections 

 seen on the internal surface of the stomach. Each of these projec- 

 tions is a canal, as may be distinctly made out, on making a trans- 

 verse section of the body and placing it under the microscope : and 

 the four canals thus formed terminate at their upper end in a cir- 

 cular canal, placed round the mouth, and near the margin of the 

 disc. Into this circular canal the hollow tentacula open. The inner 

 surface of this circular canal and of the tentacula is lined by a pro- 

 longation of the internal layer. Between the mouth and margin of 

 the disc are four round depressions, corresponding to the termina- 

 tion of the four vertical in the circular canal, which at first sight 

 appear to be four apertures opening into the circular canal ; but a 

 membrane is stretched across the bottom of each depression, suffi- 

 ciently thin to permit the ready transmission of fluids through it. In 

 certain positions of the extensible mouth, white lines presenting the 

 appearance of vessels are seen passing from the position of the cir- 

 cular canal to the margin of the mouth, and uniting with each other 

 along this margin ; but Dr. Reid has not yet been able to satisfy 

 himself that these are vessels. In some of the numerous forms which 

 the mouth assumes, these lines entirely disappear, and when pre- 

 sent they seem to be formed by narrow ridges on the external sur- 

 face. The margin of the mouth presents some indications of the 



Ann. If Mag. N. Hist. Vol. xviii. Q 



