EMBRYONIC AND LARVAL -STAGES OF THE WINTER FLOUNDER. 313 



In the latitude of New York this species is angled for in the fall and sometimes 

 as late as the middle of December. From then on it usually ceases to take the hook 

 until it is next taken in late February, the anglers' belief being that the flounders lie 

 dormant in the mud during the coldest weather. Along the New England coast the 

 fall season closes earlier and the fishes do not reappear to the anglers much before the 

 middle of March or later. Correlating this with the preceding study of the stomach 

 contents it is evident that these fish feed little, if at all, during the period of sexual 

 activity. 



The spawning act in the confinement of the hatchery tanks was invariably per- 

 formed at night, most frequently between the hours of 10 p. m. and 3.30 a. m. The 

 details of this are fully described in Copeia for January 22, 1922.' 



Embryology. — The eggs of Pseudopleuronecies americaniis are minute, adhesive, and 

 demersal. They have a modal diameter of 0.81 mm. and vary from 0.71 to 0.86 mm. 

 Due to their adhesive nature, they are frequently more or less distorted, in some cases 

 being quite ovoid ; but it is doubtful if the deformed eggs produce normal larva;. Laid 

 along a ruler, as fish-culturists measure, the eggs run 31 to the linear inch. The blasto- 

 disk (fig. 274a) is large and of a pale amber color, while the yolk is colorless. The 

 surface of the yolk is finely tuberculate, and the egg membrane resembles fine grain 

 leather in texture. The spermatozoons average about 0.030 to 0.035 mm. in total 

 length. 



At a temperature of 69 F. the first cleavage took place at about 1% hours after 

 fertilization (fig. 2746). Eggs when isolated from their companions showed flat marks 

 on the membrane where others had been adhering, some presenting the appearance of 

 fairly regular polyhedrons. Such pressure marks on the membrane appear not to affect 

 the development in any way and, being purely mechanical, are not shown in the sketches, 

 as eggs isolated from the start are perfectly spherical. The further cleavages followed 

 after the typical manner of teleostian eggs. By the time 24 hours had passed the 

 blastoderm was broken up into a high number of cells (fig. 274 c toe). By the end of 

 the third day differentiation had begun and the eggs appeared as shown in figure 274/. 

 At six days the differentiation had reached the stage shown in figure 2749, primitive 

 segmentation having commenced and the cephalic region having become more recog- 

 nizable as such. It might be noted that in many of the eggs a small sphere similar 

 to the oil globules in pelagic ova was observed, and in a few several such globules 

 were present in a small cluster. Such a structure is indicated in figure 2749. 

 Eggs beyond this stage failed to show this peculiarity. The embryo was a pale amber 

 of the same tint as the unfertilized blastodisk, and the "oil globule" was colorless. 

 Figure 274k shows the appearance at nine days. The embryo was well differentiated, 

 and chrome yellow chromatophores were sprinkled over the body, as indicated by black 

 dots. These were punctulate and difficult to see by transmitted light, but they stood 

 out prominently on a dark field. Figure 2741 gives the appearance at 15 days. The 

 chromatophores presented a similar appearance at this stage, but there was a noticeable 

 concentration of them as a vertical band in the caudal region. The heart could be seen 

 beating in slow rhythm, but no other motion was noted. The cephalic region appeared 



1 Breder, C M.. jr.: Description of the Spawning Habits of Pscudofilcuroncctes amertcamis in Captivity. Copeia. January 

 32, 1922. No. 102. pp. 3-4. New York. 



