8 Mshery Board for Scotland. 



but it does not form a long spine as in holsatus a,nd puber . These pro- 

 longations of the abdominal segments pi'obably function in connection with 

 the ecdysis of the cephalic and thoracic appendages, in which process the 

 abdomen and telson play an important part. The last Zoea (IV.) of 

 Garcinus is much smaller than the last Zoea of P. holsatus and piober, and 

 very long processes from the segments may not be required. 



Megcdops, figs. 3, 24, 27, 28. 



This stage has a short rostral spine, but no dorsal spine. It has a 

 prominently long narrow abdomen. There is a large hook on the ischio- 

 podite of the chela, and the coxopodite joint of the second, third, and 

 fourth pereiopods has a large tooth-like process {cox., figs. 28 and 24). 

 The tooth on the fourth pereiopod is turned slightly backward. The 

 hooks differ slightly in appearance when seen from difi"erent directions. 



In preserved specimens of Megalops the rosti-um is often bent down- 

 wards. The long spinous processes of the abdominal segments are absent. 

 This stage varies in size. A Megalops just cast from a Y. Zoea was 

 smaller than one which had been in this stage for some time. 



The Megalops casts into the first Young Stage. The Megalops of this 

 species is large. It is much larger than the same stage of Hyas areneus. 

 The I. Zoea of holsatus is smaller than the I. Zoea of areneus, and it has 

 a longer Zoea period, but it reaches the megalops condition in a larger 

 form than the latter. 



First Young Stage, figs. 13, 26. 



The crab which appeared as the result of the moult of a Megalops is 

 shown in fig. 13. The broad frontal region is divided into three rounded 

 portions, all of which have a minvitely crenate margin. The middle 

 portion projects a little. The antei*o-lateral denticulations of the carapace 

 are five in number. Two of these are smaller than the three others. 

 The posterior edge of each tooth is minutely serrated. The sei'ration 

 nearest the apex of the tooth is generally the largest. A few little 

 hairs are visible on the carapace, but no needle-point cilia such as are 

 present in the first young stage of Oarcinus mcenas* were made out. 

 There is no hook on the ischiopodite of the chela. The surface of the 

 chela is much serrated along ridges (fig. 26). On the side of the chela 

 there is a translucent ridge shown shaded in the figure. The abdomen is 

 now tucked in under the thorax ; the pleopods, still large, are without the 

 plumose setse. 



Second Young Stage. 



A crab of the first young stage had partly cast and died. The second 

 young stage did not appear to differ materially from the first young stage. 



PORTUNUS PUBER. 



Two berried female crabs were obtained in the Bay of Nigg in July. 

 The eggs hatched on August 13, 1900. The larvae were obtained in the 

 first Zoea stage. 



I. Zoea, figs. 4 and 49. 



CoLOURATiojsr. — The eyes appear blue to the naked eye, and so does the 

 luminous area at the base of the dorsal spine. Magnified, the eyes appear 

 covered with luminous greenish-yellow pigment. In the dead larva the 

 eyes are reddish. 



* "On the Larval and Early Young Stages and Rate of Growth of Oarcinus mcenas .^ 

 Slat Annual Report Fishery Board for Scotland, Pt. III., for 1902-1903. 



