66 DR J. H. ASHWORTH 



It is interesting to notice that all the known larvre of Pelagodiscus atlanticus — 

 about thirty altogether — have 4 pairs of approximately equal cirri.* Muller was 

 able to keep his larvae under observation in aquaria, and it is evident from his 

 accounts that they became fixed at the stage with 4 pairs of cirri. Dr Yatsu (1905) 

 found a young attached example of a related species, Discinisca l&vis, which had 

 6 pairs of cirri, so that in this species also attachment of the larva occurs at or not 

 long after the stage with 4 pairs of cirri. These facts account for the absence of free- 

 swimming stages with more than 4 pairs of cirri, but there is no satisfactory 

 explanation why earlier larvpe have not been found. Muller (I860, p. 79) 

 suggested that the youuger stages may be retained in the shell of the parent, but 

 I am not aware of any evidence in support of this view. It may be that the 

 younger stages live on the sea-bottom and hence have hitherto escaped capture ; all 

 the larvae of Pelagodiscus recorded have been taken at or near the surface. 



Breeding Season. — Few data are available on this point. Professor Blochmann's 

 specimens were collected off Bintang on July 3, 1899, and mine were taken off Cape 

 Comorin on October 16, 1914. Dr Yatsu does not state when he found his 

 specimen, but, as it occurred among the larvae of Lingula at Misaki, it must have 

 been in the period from the latter part of July to the middle of September. 



Muller states that at Desterro, Brazil, the larvoe occurred in late summer, from 

 February to April, a season which corresponds approximately with the period in 

 which the larvae have been found in the northern hemisphere. 



LIST OF LITERATURE. 



Blochmanx, F., " Die Larve von Discinisca" Zool. Jahrb., Abt. Auat., Bd. xi, pp. 417-426, Taf. 31, 1898. 



Blochmann, F., " Unter.s. liber den Bau der Brachiopoden," ii. Jena, 1900. 



Bhooks, W. K., "The Development of Lingula," Chesapeake Zool. Lab. Sc. Results of 1878, pp. 35-112, 



pis. 1—6. Baltimore, 1879. 

 Eichler, P., " Die Brachiopoden der deutsclien Siidpolar-Exped.," D. Siidp.-Exped., Bd. xii, Zool., iv Bd., 



pp. 384, 385, Taf. 44, Fig. 22, 1911. 

 M'-Ckauv, J., " On the Lingula pyramidata described by Mr W. Stimpson," Amer. Journ. Sci. and Arts, 



2 ser., vol. xxx, pp. 157, 158, 1860. 

 MORSE, E. S., " Embryology of Terebratidina," Mem. Boston Xoc. Nat. Hist., vol. ii, pp. 249-264, 1873. 

 MORSE, E. S., Proe. JJoston Soc. A r at. Hist., vol. xix, p. 266, 1878. 

 MULLER, F., " Beschreibung einer Brachiopodenlarve," Archivf. Anat. Physiol., Jahrg. 1860, pp. 72-80, 



Taf. i. 

 MULLER, F., "Die Brachiopodenlarve von Santa Catharina," Archivf. Naturgesclh., Jahrg. xxvii, Bd. i, 



pp. 53-56, 1861. 

 SEMPER) C, " Rcisebericht," Zeilschr. wiss. Zool, Bd. xi, pp. 103, 104, 1861 ; Bd. xiv, p. 424, 1864. 

 Skwell, R. B. S., " Note on the Development of the Larva of Lingula," Records Indian Mus., vol. vii, 



pp. 88-90, 1912. 



* Excepl I lie abnormal specimen mentioned on \>. 62, which has only three cirri on the left side. 



