130 Literary and Philosophical Society of St. Andrews. 



without their dividing into young Medusae. Towards the end of 

 July the larvae ceased for a short time to reproduce themselves by 

 buds and stolons, but by the beginning of August they were again 

 propagating themselves in this manner, though less actively than in 

 April and May. On the 10th of February last, the upper part of 

 some of the larvae had become elongated, cylindrical, of considerably 

 diminished diameter, with transverse rings commencing at the top. 

 Each of these transverse rings developed itself, in the manner that 

 Sars has described, into a young Medusa, having eight bifid processes 

 projecting from the margin of the disc. In many of the larvae, while 

 the upper part of the body was of a reddish brown colour, and was 

 splitting itself into as many as thirty or forty young Medusae, the 

 lower part was of its usual white colour, and was reproducing new 

 larvae by means of buds. In no case in which the process of splitting 

 was watched, did the whole of the larva break itself up into young 

 Medusae, but a portion, often very small, at its attached extremity, 

 continued to live as a larva, and threw out new tentacula before the 

 last of the young Medusae, into which the rest of the body had split, 

 had been detached. Dr. Reid then gave a detailed description of 

 these young Medusae, and explained their structure as seen under 

 the microscope. Among other things, he stated that the appear- 

 ances described by Steenstrup as vessels in the young Medusa, at 

 the period of its separation from the larva, are merely ridges on its 

 lower surface. Cilia were observed on the inner surface of the 

 mouth, stomach, and on the surface of four remarkable double pro- 

 cesses adhering to the inner surface of the stomach. The ocellus, 

 as it is termed, placed in the cleft of each of the eight processes pro- 

 jecting from the margin of the disc, is chiefly made up of several 

 cylindrical crystals, presenting several interesting appearances not 

 hitherto described. 



Dr. Reid also stated, that since his last communication on this sub- 

 ject to the Society, he had made additional observations on the loco- 

 motive powers of the larvae. The young larvae developed from buds 

 generally move to some little distance, sometimes a considerable di- 

 stance, from the older larva which formed these buds, even after they 

 have been fairly detached from their parents. This locomotion is 

 slow, and is effected by a kind of sliding motion of the attached end 

 over the substance to which it is fixed. Dr. Reid had also observed 

 very minute cilia on the external surface of the bodies of some 

 larvae*. 



* A delay in the publication of the Abstracts of the ' Transactions' of the 

 Society enables Dr. Reid to add, that the larvae ceased to split into young 

 Medusae about the end of the first week in May ; that the surface of the 

 stones are as thickly covered with them at present (30th May) as before they 

 began to split, so that he has now kept this colony of larva; above 20§ months, 

 and it was not until they had been 17| mouths in his possession that some 

 of these larvae began to split into young Medusae, while many of them have 

 not yet done so at all. These observations of Dr. Reid confirm some of 

 those made by Sir John Dalzell on the larvae of the Medusa, under similar 

 circumstances (vide Jamieson's Philosophical Journal for 1836), and differ 

 very considerably from some of those made by Sars and Steenstrup upon 

 these animals, placed under different conditions. 



