4 Fishery Board for Scotland. 



Portunus. 



The three species which are here dealt with, viz., holsatus, puher, and 

 dejiurator, have Zoeae which exhibit many points of resemblance. The 

 carapace has four spines, viz., a rostral, dorsal, and two lateral. The 

 dorsal and rostral spines are plain, without serrations, and the dorsal is 

 markedly curved. 



Cano* was of the opinion that there were three Zoea stages and two 

 Megalops stages in this genus. I am of the opinion that there may be five 

 Zoea stages, but only one Megalops stage. Cano's three Zoea stages 

 correspond to my 1., lY., and V. stages. He pointed out that the spinous 

 prolongations of the hind border of the third, fourth, and fifth abdominal 

 segments are absent in the I. Zoea, but appear in his second Zoea stage. 



Portunus holsatus, Fabr. 



Colour of Larvce. 



The larvae of this form hatched on July 19, 1900. They were, in 'the 

 protozoea stage (fig. 7). The pigmentation of the protozoea was of service 

 in enabling me to recognise among the Plankton Zoea stages belonging to 

 this species. The colours present ai-e yellow and black. There ai-e two 

 black stellate corpuscles on the side of the carapace near the position of the 

 base of the lateral spine. A small bright yellow spot is situated dorsal to 

 the eye. Tho black retinal portion of the eye is surrounded by a deep 

 yellow network, from which a delicate yellow tracery extends over part of 

 the anterior surface of the eye. None of the protozoese lived to cast into 

 the I. Zoea. For the Zoea and Megalops stages I therefore made use of 

 plankton material. 



The Zoese, which were obtained by the Garland in the Moray Firth, 

 were of a general dark colouration. A large quantity of brown pigment 

 was present in the cephalothorax. The cephalothoracic mass is also dorso- 

 laterally slightly greenish-coloured. To the naked eye this region was by 

 reflected light almost black, when the dark brown pigment was dense. 

 The eyes are blue, and they are covered with luminous yellow. A bluish- 

 yellow luminous spot is situated medially just behind the eyes. On the 

 under surface of the abdomen, and especially at each point, there was a 

 large quantity of brown pigment. Yellow pigment accompanies the biown 

 in certain parts. 



In a TV. Zoea the joints of the maxillipedes were touched off with pink. 

 The dorsal spine had sortfe amber pigment about the middle of its length. 

 A V.-stage Zoea showed thi-ee bronze-blue luminous areas round the base 

 of the dorsal spine. One was situated in front, and one on either side. 

 On the side of the carapace there was a large yellow area. The eyes were 

 very blue. 



Megalops. 



Specimens of the Megalops stage were obtained on 23rd June. They are 

 dark, with blue eyes. They show on the dorsum of the cephalothorax two 

 luminous lemon -yellow spots in the middle line. The larger, which is 

 posterior to the less, may be resolved into two spots (fig. 3). The 

 stomachial region is pigmented a dark brown, and brown patches are 

 present on the lateral regions of the abdominal segments and on the lateral 

 region of the carapace. 



*Cano: " Sviluppo dei Portunidi. Morfologia dei Portunidi e Corystoidei. " 

 Memoria di Matematica e difisica della Socirta Italiana delle Scienze idetta dei XL.). 

 Serie 3a, T. VIII. 



