SPECIES NO. 28. 



Length 2.00 mm. 



Yolk-sac (ovoid) SO X .+7 " 



Yolk-sac to vent 10 " 



Vent to tii> .95 " 



Width of head 30 " 



Dimensions of Fig. 5 : — 



Length 3.00 mm. 



Yolk-sac 60 " 



Yolk-sac to vent 20 " 



Vent to tip 1.90 " 



Species No. 28. 



Plate I. Figs. 6-8. 



Our knowledge of this species is limited to what could be learned from 

 a single ess, found August 15, 1881* This is the smallest of the ea-o-s 

 described in this paper, measuring only .03 mm. by .05 mm. The oil-globule 

 is also diminutive in size, being only .085 mm. in diameter. 



Shortly after the closure of the blastopore (Fig. 0) the yolk and embryo 

 are very transparent, the only pigment being a few small, round black dots 

 (about .005 mm.) scattered over tbe dorsal surface of the embryo and the 

 yolk-sac in the neighborhood of the globule. 



Thirty hours later, at the time of hatching, the pigment consists of 

 scattered black dots, yellow dots, and four round black spots, placed as 

 shown in Fig. 7. A few black and yellow dots are seen on the oil-globule, 

 but none on the yolk. 



Dimensions taken from Fig. 7 : — 



Length 2.10 mm. 



Yolk-sac 70 X -35 " 



Yolk-sac to vent . . 0.5 " 



Vent to tip 1.20 " 



Height 45 " 



Width of head 225 " 



The specimen represented in Fig. 8 was taken in September, 1883, and 

 is probably a somewhat older stage than that of Fig. 7. The lateral position 

 of the vent makes it quite certain that this specimen, if normally developed, 

 docs not belong to the same species, in other respects, however, there 

 is a close resemblance, allowing foe the fact that Hie yellow pigment is 

 expanded in Fig. 8 ami contracted in Fig. 7. 



* The egg ami young of tl have also been taken this season (Julj 6, IS85) hj Mr \gassiz. 



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