No. i.] REPRODUCTIVE ORGANS OE DWPATRA. 1 1 5 



the high temperature experienced at Beaufort, seems to rapidly 

 set up degeneration in the cells. 



In the ripe ovum 600 /x. in diameter, as already noted, the 

 green pigment is aggregated about a clear area 125 /j,. in diame- 

 ter. On section of the ovum it is found that this is a clear 

 protoplasmic part intervening between the eccentric nucleus and 

 the thick egg membrane. The relation of the clear region, the 

 nucleus with its peripheral nuclei, and the green pigment, is 

 shown in the section, Fig. 4. The main mass of the ova is filled 

 with large, round yolk bodies imbedded in a fine granular or 

 reticulated protoplasmic matrix, while the clear area, a, alone is 

 entirely free from yolk and from pigment also. The yolk is not 

 found in ova 100 fi. in diameter, and must therefore be formed 

 while the ovum and its appendages float freely in the body-cavity 

 liquid : younger eggs are uniformly granular throughout, though 

 the peripheral part of the protoplasm is easily affected by re- 

 agents, and seems less solid than that nearer the nucleus. In 

 fresh material the egg membrane is seen to be perforated by 

 innumerable pores, though not seen in sections. 



That the egg as represented in Fig. 4 is ripe seems indicated 

 by its size, occurrence in great numbers, packing the body cavity 

 full, and by the occasional finding of like eggs amongst the 

 larvae of this season of the year in the gelatinous egg masses : 

 yet attempts at artificial fertilization were unsuccessful. 



These larvae are spherical, at the earliest stage obtainable at 

 this time of year, and revolve within the jelly by equatorial and 

 terminal cilia. Each is only about 550 //.. in diameter in pre- 

 served specimens, and retains the egg membrane as a cuticle 

 5 /x. thick. At this early stage the body is sprinkled over with 

 irregular green patches of pigment, derived in all probability 

 from the green pigment of the egg. 1 



1 The remarkable slimy gelatinous egg mass of D. magna forms a conspicuous and 

 common cylindrical slender body, several feet long, lying on the sand where the adult 

 lives. The larvre found in this gelatinous common envelop have been figured and 

 described by Professor Wilson (Studies Biological Laboratory, S.H.V., Vol. II, 1883) 

 as belonging to D. cuprea. 



The production of these great gelatinous masses is undoubtedly accomplished by 

 the secretion of unicellular, epidermal glands along the lateral aspect of the pos- 

 terior region of the body of the female, where there are two white, swollen masses 

 of epidermal cells both anterior to and posterior to each parapodium. 



These masses readily swell in water and produce the above jelly : one of them 

 seems to surround the nephridial opening. 



