MUSEUM OF COMPARATIVE ZOOLOGY. 109 



Observations. 



Plate I. Tigs. 1-93. 



The material upon which my observations were made was collected at 

 Eastport, Maine, in the summer of 1885. Adult Ophiopholes were 

 dredged off Friar's Head, Campobello. Great numbers were taken just 

 below the line of low tide on Clarke's Ledge, near Eastport. 



The following observations on the development of the egg were begun 

 after its fertilization, and after it had been laid. 



Ova were voluntarily cast by the female on the 1 7th of August. They 

 were found in multitudes at the bottom of the glass dishes in which the 

 adults were confined, forming a greenish or yellowish cloud discoloring 

 the water. A white fluid of spermatozoa was also found in another dish 

 containing males. As both elements are cast in the water it is probable 

 that in this species fecundation occurs outside the body,* as is generally 

 the case among Echinoderms. The ova of Ophiopholis, like the adults, 

 appear to be very hardy, and very little care is necessary to keep them 

 alive. The contact of sperm and ova was not observed. The white fluid 

 containing spermatozoa was mingled with fluid containing ova, and it is 

 thought that artificial fecundation was thus effected.f The ova began 

 to develop soon after. Fecundated ova were also found in water in 

 which many Ophiopholes were living. 



Each egg, PI. I. fig. 1, is enclosed in a transparent capsule .13 mm. in 

 diameter. This capsule in the first stages observed was not thick as in 

 the viviparous genus, Amphiura, but very thin. It is thought to be 

 homologous with the outer layer, m c, mentioned and figured in Metsch- 

 nikofi"'s account J of the development of A. squamata. Its thickness 

 may have been greater in younger stages. The eggs are not laid in 

 bunches, masses, nor were they observed to be cemented together. They 

 were not observed to develop in pouches, although pouch-like parts of 

 the genital glands, ovaries, are sometimes squeezed out through the geni- 

 tal slits as in the genus, Gorgonocephalus. When the ova were first 

 examined segmentation had not begun, but no germinative nucleus was 

 seen. Each egg in the youngest stage, PI. I. fig. 1, has the yolk com- 



* In Amphiura fecundation takes place in the body, teste Apostolides, Metsch- 

 nikoff, and others. 



t Metschnikoff {Zeit. f. Wiss. ZoSL, XLIL p. 664), artificially fertilized Ophio- 

 thrix fragilis. 



X Op cit., p. 14. Plate III. Fig. 3. 



