45 



III.- — On Larvae of Lingula and Pelagodiscus (Discinisca). By J. H. Ashworth, 



D.Sc, Lecturer in Invertebrate Zoology in the University of Edinburgh."* 



(Received March 15, 1915. Read March 15, 1915. Issued separately November 19, 1915.) 



[Plates IV and V.] 

 CONTENTS. 



The Larvae of Lingula 46 



Previous Records of the Larvae of Lingula 



(s. lat.) 46 



The Larvae of Lingula anafina ... 47 



Localities 47 



Description of the Larvae ... 47 



(i) Larvae with 8-10 pairs of Cirri . 47 



(ii) „ 11 „ .49 



(iii) „ 12 „ . 49 



(iv) „ 13 „ . 50 



(v) „ 14-15 „ . 52 



Comparison of the Larvae with those pre- 

 viously recorded 54 



Breeding Seasons ...... 56 



Comparison of the Larvae of Lingula anatina 



with Brooks's Larvae of Glottidia audebarti 56 



The Larvae of Pelagodiscus (Discinisca) . . .58 



Previous Records of the Larvae of Discinidce . 58 



TheLarvaeof Pelagodiscus(Discinisca)atlanticus 59 



Description of the Larvae ... 60 



List of Literature 66 



Description of the Plates 67 



The specimens which form the subject of this paper were collected on voyages to 

 and from Australia on board the s.s. Orsova and Otway of the Orient Line. Sea- 

 water was being constantly pumped on each ship, by a rotary pump, from an inlet 

 about 18 feet below the water-line to a large tank on the boat deck, and I was 

 allowed to run off, through a plankton net, as much of the water as I desired in order 

 to collect the organisms contained therein. For this privilege, of which I availed 

 myself to a liberal extent, I beg to thank Captain J. F. Healey and Captain F. S. 

 Symons. The small organisms suffered comparatively little by their passage 

 through the pump and pipes, and were, for the most part, in a living and active 

 condition when examined. 



The larvae of Lingula have been so seldom recorded that the occurrence of 

 fourteen larvae of Lingula anatina in the catch made on June 21, 1914, in the 

 southern part of the Red Sea, was noteworthy. On the return journey, in October, 

 careful watch was kept for others, and one larva of Lingula anatina was taken in 

 the Indian Ocean, about 4° south of Colombo, two others in the southern portion of 

 the Red Sea, and six larvae of Pelagodiscus [Discinisca) a little to the west of Cape 

 Comorin. The larvae were examined microscopically immediately after capture, and 

 were then preserved in formalin, which has proved to be a satisfactory fixative. 

 Most of the specimens have been stained in haematoxylin, cleared, and mounted as , 

 whole objects, for which their depressed form and transparent shell and mantle 

 render them very suitable ; six larvae have been cut into serial sections. 



* A grant in aid of the expenses incurred during this research has been received from the Earl of Moray Endow- 

 ment of the University of Edinburgh. The cost of reproduction of the plates has been defrayed by the Carnegie 

 Trust for the Universities of Scotland. 



TRANS. ROY. SOC. EDIN., VOL. LI, PART I (NO. 3). 8 



