1889.] Days and Nights by the Sea, 4^9 
ting bells of ghost-like jelly-fish, rising and falling as they 
deliberately contract and expand their discs ; the floating Si- 
phonophorse transparent as the air and delicate as spun glass. 
In the turmoil of the moment a thousand strangely beautiful 
forms pass rapidly before the eye. 
The larvje selected for study are carefully set aside in beak- 
ers of sea water, or in watch glasses, and it is sometimes possi- 
ble to keep them alive for a number of days, and observe their 
transformations, but usually unless there is means of providing 
them with freshly aerated sea- water, this is not possible. Some 
forms are so delicate that one is hardly able to bring them in . 
alive. They die as soon as caught. 
Where it can be done, by far the most satisfactory method of 
studying the development or life history of an animal is to 
procure the adults and keep them under observation until they 
deposit their eggs. The development of the ova can then be 
studied with the closest detail, not only by the superficial view 
of the growing embryo, but by means of the sectional method 
which has yielded such valuable results to natural science in 
the past ten years. 
In the case of many animals, such as fishes, "king crabs," 
oysters, starfish, and sea urchins, where the sexes are separate, 
the ripe eggs can be obtained and fertilized artificially, and 
the complex processes by which the highly organized fish or 
mollusc is slowly built up by changes which start in the germ 
cells, can be witnessed in all their details. Animals difi"er very 
widely in this respect however, and the vitality of the ova is 
connected in some cases certainly with that of the animals 
themselves. Starfish or Ophiurans may be sadly mutilated 
without killing them, and some of the molluscs are notoriously 
hardy. A year and a half ago I brought from the West Indies 
a collection of marine shells, gathered in the water or on the 
coral rocks on shore. They were done up in a package 
and sent with other collections to my home in New Hamp- 
shire. The next fall when the bundle was opened, much to 
my surprise a number of the univalves {Tectarius niuricatus), 
were alive and crawling about. In one of our eastern colleges. 
