386 MARGARET ROBINSON. 



tneridionally, resulting in four cells. These again divide 

 longitudinally. At first the cells only cover the lower pole 

 of the egg forming two rovp^s of cylindrical cells. Later they 

 spread over the whole egg." 



Then follows a description of seven stages in development. 

 In the last of these only does the embryo become a true larva 

 — for here alone it is free swimming ; the other stages being 

 passed through in the brood pouch of the mother. 



First Stage. — In the first of these stages he notes a 

 thickening on the ventral surface and the first appearance of 

 the papilla. 



Second Stage. — He describes an embryo with nauplius 

 appendages, and an abdominal papilla which is bent over the 

 ventral surface. In this stage he also notes the appearance 

 of the endoderm and the way in which it begins to grow round 

 the yolk. 



Third Stage. — He notes two pairs of maxillae and two 

 thoracic legs, as well as the nauplius appendages. Here, too, 

 he observes mouth and stomodaeum, as well as anus and 

 proctodaeum. 



Fourth Stage. — He describes the change in position of the 

 appendages (they are now directed backwards instead of out- 

 wards), and the appearance of the third thoracic limb. He 

 also notes the possession of dorsally directed palps by the 

 maxilla and thoracic appendages. In this stage, too, there 

 is an increase in the size of the optic lobes and brain, and 

 here he first describes the labrum. In each of these two last 

 stages he describes the further circumcrescence of the yolk 

 by the endoderm. He remarks, too, on the different appear- 

 ances of the yolk in different places; that which is still not 

 enclosed by endoderm being dense and granular, while the 

 enclosed portion seems to be liquid and contains but few 

 granules. 



Fifth Stage. — The embryo now bursts the vitelline mem- 

 brane, but is still enveloped by a cuticle, and the abdomen 

 springs back so that now instead of lying on the ventral sur- 

 face it is slightly curved in a dorsal direction. The cuticle 



