CORONAT.E — NAUSITHOK. 



555 



subunibrella; the 4 lips are without prominent oral appendages or palps. The central 

 stomacli is connected with a wide annular sinus in the disk by means of 4 wide, perradial ostia, 

 alternating with which there are 4 short interradial septa (see Claus, 1883, p. 27, tat. 7, fig. 48). 

 The broad ring-sinus is interrupted near the bell-margin by 16 septa in the radii of the mid- 

 axial lines ot the lappets. These septa are not complete, however, but leave a marginal 

 ring-canal. Thus the 16 peripheral stomach-pouches are in the radii of the sense-organs and 

 tentacles, and are joined bv the marginal ring-canal in the axial line of each lappet. 



Four groups ot simple, unbranched, gastric cirri are upon the interradial septa of the 

 central stomach and project centripetally inward into the central stomach; altogether there 

 are about 28 gastric cirn, about 7 in each group. The 8 adradial gonads occur in the 8 ten- 

 tacular radii and are upon the floor ot the subumbrella in the zone ot the wide, inner ring- 

 sinus of the bell. Each gonad is large and globular and consists of a pocket-like fold of the 

 entoderm of the subumbrella (see Claus, 1883, p. 31). A zone of well-developed circular 

 muscle-fibers is on the subumbrella between, and centrifugal to, the gonads. Centripetal 

 to this, powerful strands of radiating muscle-fibers extend outward to the tentacles and mar- 

 ginal lappets; also, 8 poorly developed strands ot radiating muscles extend outward in radial 

 and interradial positions from the base of the oesophagus to the zone of circular muscles. 

 The color of this medusa is quite variable. The gelatinous substance of the bell is usually 

 translucent-milkv, greenish, or light brownish. The gonads are brownish or red or, in the case 

 of the males, bright yellow. Rosin-colored spots in the ectoderm ot the exumbrella, especially 

 upon the lappets, are due to clusters of small cr\stals (see Claus, 1883, fig. 44, tat. 6). 



A young ephyra of this species was found b\' us near Flamingo Key, Bahama Islands, 

 February 9, 1893. It was 2 mm. in diameter, and there were as yet no marginal tentacles 



and only 4 gastric cirri A slightly older ephyra has been figured 

 by Claus, 1883, fig. 48, taf. {. 



This medusa is a surface form, and is common in the Med- 

 iterranean, Atlantic, Pacific, and Indian Oceans, and in all trop- 

 ical or warm seas. Naiisithoe polaris {Nauphanta polaris 

 Fewkes) from the Arctic Ocean, appears to be identical with 

 N. punctata, and if this be true Vanhotfen is right in stating 

 that Nausithoe punctata is found in all oceans. It is abundant 

 in summer at Tortugas, Florida, and in the Bahamas, but has 

 not been found on the Atlantic coast of the United States north 

 of the Carolinas. Vanhoffen, 1906, describes a specimen 12 mm. 

 wide from N. lat. 59° 39', W. long. 8° 49'. 



Hamann, 1883, studied the development of the ephyra of 

 this species and finds that the gonads first appear as 4 inter- 

 radial entodermal swellings in the subumbrella wall of the 

 stomach, at a time when the ephyra has but one gastral filament in each interradius. Later 

 the 4 original gonads divide and migrate so as to become 8 in the adradii of the subumbrella 

 wall of the stomach. The genital products originate in the entoderm and migrate into a gelat- 

 inous space between two layers of entoderm. The spermaries appear as a series of follicles 

 in this space. 



According to Metschnikoff, 1886, who has studied the early development of Nausttho'e 

 "marginata" (which is apparently identical with N. punctata) the egg is citron-yellow, 0.23 

 mm. in diameter, and is laid in mid-day in December; segmentation is total but somewhat 

 unequal, the cells of the vegetative pole being largest. A wide, central, cleavage cavity is formed 

 and the gastrula results from invagination at the hinder end of the larva. The blastopore 

 then closes over and the entoderm is entirely inclosed by a layer of ciliated ectoderm, and 

 the free-swimming planula is thus formed. 



The remarkable sc\phostoma larva of N^ausitho'e punctata bears a striking superficial 

 resemblance to a hydroid and it lives commensal within sponges such as Suherites, Myxilla, 

 Reneira, Esperia, etc. It is especially abundant at Trieste and Naples. This hydroid-like 

 larva forms a branching tree-like growth within the body of the sponge, the pohp-mouths 

 and their tentacles projecting out of the oscula of the sponge. The branching, tree-like stock 

 of the larva is covered with an irregularly annulated, chitinous perisarc, which terminates 

 at a short distance below the zone of tentacles of each polypite. The mouth of the polypite 



Fig. 31^4. — ^^ Nauphanta'^ albatrossi, 

 after Maas, in Mem, Mus.Comp. 

 Zoolog)' at Harwird College. 



