CORONATiE — LINUCHE. 559 



in 3 zones (text-fig. 356a). The 2 inner rows are each composed of 8 large perradial and 

 interradiai saccules which lie between the gonads, the 8 innermost saccules being partially 

 cleft and bean-shaped (plate 59, fig. 7); a third row of 32 smaller saccules, 2 for each lappet- 

 pouch, lies at the level of the outer ends of the horns of the crescentic gonads. In the sub- 

 umbrella we find a broad, unitary, marginal area of ring-muscles, and centripetal to this are 

 more or less isolated strands of radial muscle-fibers. 



The entoderm of the gonads, of the wart-like saccules, and of numerous, separated, 

 more or less polygonal areas oi digestive cells in the gastric pouches is brown. 8 rows of 

 dark-brown spots extend longitudinally down the inner surface of the lips. 



Vast numbers of the ephyrae of this medusa appear among the Bahama Islands and 

 West Indian region in February and March, and become mature from April until early June, 

 usually disappearing at or about the middle of May. I have seen hundreds of such swarms, 

 all composed of but one species. I have never seen any of the so-called "species" described 

 by Haeckel from the West Indian region, and it appears to me that he has constituted species 

 out of preserved material displaying various well-known characteristics of abnormal con- 

 traction and in various stages ot growth. In fact I have seen Haeckel's "species" only in 

 medusae which I have myself preserved. They appear'not to exist except in alcohol. 



In the Bahama-Florida region in spring these medusae form swarms, miles in extent, 

 filling the water with myriads of brown thimbles, all actively spinning clockwise as they 

 progress through the water. 



Conklin, 1908, has studied the habits and early development of Linuche iinguiculata. 

 When mature the medusae rise in vast swarms to the surface and the eggs are discharged and 

 fertilized at 8 p. m. The female gonads are slaty or blue-gray in color while those of the male 

 are brown. When the gonads have been emptied the medusae sink down to the bottom and 

 die. Each egg is closely invested by a very thin transparent membrane which persists to the 

 gastrula stage. The eggs are laid near the surface but gradually sink downward. The newly 

 laid egg is 0.24 mm. in diameter. It consists of a peripheral layer of clear protoplasm, an 

 intermediate la}er of densely packed yolk spherules, and a central sphere composed appar- 

 ently of dissolved yolk. The peripheral layer becomes the peripheral layer of the blastula and 

 gastrula, and gives rise to the cilia of the ectoderm. The intermediate "shell" of closely 

 crowded yolk spherules constitutes the principal part of all of the cells of the gastrula and 

 blastula, while the central mass of dissolved yolk is poured into the cleavage cavity and probably 

 serves as a source of nourishment for the surrounding cells. 



Two polar bodies are formed. The first two cleavages are meridional and cut downward 

 from the anmial (polar body) pole to the vegetative pole, and the third cleavage is equatorial. 

 Up to the 64-cell state the divisions are wholly mitotic. Cleavage is total and practicall)' equal. 

 When the embryo consists of about 1,000 cells protoplasmic processes appear over the entire 

 periphery, and these push off the egg membrane and form the vibratile cilia. Gastrulation 

 usually takes place by invagination of the small, rounded cells of the vegetative pole of the 

 embryo; but sometimes there is a unipolar ingression of cells at the vegetative pole and no 

 invagination. The blastopore closes so that the entoderm becomes entirely incased within 

 the ectoderm, and the larva elongates and becomes a free-swimming planula. 



Isolated blastomeres, at least as late as the 4-cell stage, may give rise to apparently normal 

 free-swimmins larvae. 



The center ot the egg is more nearly fluid than the peripheral layers, and this fact favors 

 the cutting inward of the cleavage furrow from the animal pole to the vegetative during the 

 first two divisions, and the unilateral constriction in the third (equatorial) division. 



When the ephyra is 1.5 mm. in diameter, it has 16 lappets and 8 sense-organs, but neither 

 tentacles nor gonads. 4 gastric cirri, one i*each interradiai side of stomach. Disk very flat, 

 brown in color (fig. 3, plate 59). When 3 mm. wide the tentacles begin to develop, and the 

 gonads appear when the medusa is about 5 mm. wide. The polygonal areas of pigmented 

 digestive cells then develop in an inner ring of 16 large areas centrifugal to the gonads, and 

 still farther out an outer annulus of 32 areas. There are also irregularly shaped and arranged 

 areas of brown cells in the lappets (plate 59, fig. 5). The subumbrella saccules do not develop 

 until later. 



