40 GL O. Sars. 



bridge, thus indicating the rapid rate in which 

 the cleavage takes place. 

 Fig. 10. First gastrula-stage. The blastoporus is seen at 

 the lower pole of the egg, encircled by 8 cunei- 

 form ectodermal cells. 



» 11. Another egg in the same stage, with the gastral 

 pole turned to the observer. 



» 12. More advanced gastrula, with the gastrula-mouth 

 turned downwards. The dark-coloured mesoderm 

 can be faintly traced through the ectodermal layer. 



» 13. Embryo with the first intimation of the Nauplian 

 limbs; dorsal view. 



» 14. Ideal section through an ovum in the 1st gastrula- 

 stage, showing the ectodermal layer, the central 

 entodermal cells, and the mesoderm in process of 

 formation. 



Plate 3. 

 (All figures drawn from fresh specimens). 



Fig. 1. Oosphère with enclosed embryo in its last stage; 



magnified SO diameters. 

 » 2. Recently hatched Nauplius, viewed from the 



ventral face; same amplification. 

 » 3. More advanced Nauplius, viewed from the dorsal 



face; magnified 76 diameters. 

 » 4. Last Nauplian stage, viewed from the ventral 



face; same amplification. 

 » 5. A mandibular leg of same, more highly magnified. 

 » 6. Larva in the Metanaujilius-stage, viewed from 



the ventral face; magnified 70 diameters. 



