A POST-PUERULtlS STAGE OF JASUS LALANDII. 189 



A Post-Puerulus Stage of Jasus lalandii (Milne Edw.), Ortmann. By 

 J. D. F. Gilchrist, M.A., D.Sc, Ph.D., F.L.S., Professor of Zoology 

 in the University of Cape Town. 



(Plates 15 & 16, and 13 Test-figures.) 

 [Read 3rd April, 1919.] 



Since the description of the early larval stages of the Cape Crawfish in the 

 Journal of the Linnean Society (4, 5) further information has been obtained 

 and may be put on record. It is now possible also to compare the results 

 with what has been done in the case of the New Zealand Crawfish, which, 

 after careful examination by Miers, Haswell, Parker, McCoy, and Ortmann, 

 is now accepted as identical with the Cape species. Some of the early stages 

 of this have been noted by Thomson (8), Caiman (3), Archey (1), while 

 Gruvel (6, 7) and Bouvier (2) have directed attention to young stages found 

 at the Island of St. Paul, thus affording -material for comparison and the 

 further building up of the life-history of this widely distributed crustacean. 



The object of this note is the filling in of another gap in the life-history, 

 by a description of the stage immediately succeeding the puerulus stage, and 

 representing the transition to the adult form, but differing from it in some 

 respects. This was rendered possible by the procuring of living specimens 

 in the puerulus stage, and rearing them to the next stage. This afforded 

 also an opportunity of observing the habits of the puerulus, which may be 

 first noted. 



The specimens were procured by trawl in Table Bay on four occasions in 

 the months of November and December in 5 to 14 fathoms of water, and 

 were transferred to the Marine Laboratory at St. James near Cape Town. 

 They proved to be very active animals. When placed in the tank, thev 

 immediately darted to the bottom by a strong flexure of the tail, and hid 

 themselves below the weed and stones placed there. When driven out of 

 these places they quickly sought refuge elsewhere, sometimes on the under 

 surface of some weed floating at. the surface of the water. Contrary to 

 what was expected, they were never observed to swim about by means of 

 their abdominal appendages, -which are specially well developed at this stage, 

 as if for this purpose. They seem to be vegetarian in their habits, as they 

 fed on the seaweed, but not on animal food placed beside them in the tank. 

 The flesh of fish, crabs, and molluscs was offered them, but they paid little 

 or no attention to it. 



The most noticeable change observed was in the colour. When first 

 procured they were very transparent, with the exception of a few bright 

 spots of a reddish colour on the under side of the body. After about three 

 days in the tank, some of them were observed to be assuming a darker shade, 



LINN. JOURN. — ZOOLOGY. VOL. XXXIV. . 15 



