1876 MEDUSA 29 



the weather has been so stormy that no jelly-fish 

 could be got. 



The most interesting observations I have made 

 since writing before are the following. Unmutilated 

 Sarsia in a dark room seek a beam of light thrown 

 into the bell- jar containing them, and this as keenly 

 as do moths. But when the so-called eye-specks are 

 cut out, the animal no longer cares for light. 



I have only come across two species of luminous 

 Medusae — both, I beheve, as yet undescribed — and in 

 these the light is emitted from the margin alone, and, 

 with electrical stimulus, is strictly confined to the 

 intra-polar regions, being strongest at the two 

 poles. 



There is no doubt at all about the muscular 

 nature of the fibres we saw. In the larger kinds of 

 MedussB (the covered-eyed) these fibres are much 

 coarser, and are clearly seen to be arranged in con- 

 centric bundles, having four or five fibres in each 

 bundle. Alternating with these bundles, and about 

 the same width as these, are strands of undifferen- 

 tiated protoplasm. These strands are not sponta- 

 neously contractile, although their dimensions are 

 altered by the contraction of the muscular branch 

 on each of their sides. No part of the tissue is 

 doubly refracting in the fresh state. Is there any 

 way of treating it with a view of bringing out this 

 property if latent, so to speak ? The peculiarity is 

 not due to the transparency of the tissue, for I find 

 that the muscular fibre of the transparent osseous 

 fish Leptocephalus is as doubly-refracting as could be 

 wished. There are no signs of striae, but Agassiz 



