1904. Kanb. — Further captures of My sis relicta in Irelaiid. 109 



portion of this large sheet of water, Its absence from Lough 

 Mask, as well as Lough Conn, Lough Melvin, and Lough 

 Oughter, of which I have convinced myself, seems to me very- 

 significant, as bearing on Loven's theory of its marine 

 origin and introduction ; but before drawing any conclusions, 

 I am anxious to gather more facts, and to extend my re- 

 searches to the Shannon, Lough Derg, Killarney, and the 

 Mullingar lakes. Up to the close of 1903, the largest Irish 

 specimens I had met with measured . from the tip of the 

 antennal scales to the extremity of the telson 20 to 22 mm. 

 Being desirous to ascertain the maximum growth attained, 

 and to know something about the winter development of the 

 ova and young, I procured some specimens in Upper Lough 

 Brne on the nth February ultimo. On the ground where 

 they had been plentiful in past summers none were taken, 

 but two short hauls in the deepest hole in that portion of the 

 lake produced 28 female specimens, showing that probably 

 they frequent deeper water in winter. No males were seen. 

 The average size was considerably greater than any that I 

 had yet seen. Four selected at random measured 22, 23, 23, 

 and 24 mm. respectively, the latter being within i mm. of 

 the length of those from Lake Onega recorded by Czerniavski. 

 A mass of embryos in various stages of development dis- 

 tended the incubatory pouches. The auditory organs in the 

 pair of caudal lamellae were distinctly represented by dark 

 spots (see fig. 2, a), and from two to four similar spots in some 

 specimens on the sides of the ventral region of the abdomen, 

 near its junction with the cephalothorax, indicated the 

 incipient abdominal ganglia. Van Beneden has described 

 the embryology of the genus, but it is possible that no data 

 have been hitherto available as to the condition of develop- 

 ment of M. relicta at this season, since other European 

 habitats in the fresh waters of Scandinavia, Finland, Russia, 

 &c., would probably be frozen over in February. 



Drumreaske, Mouaghan. 



A 3 



