FKOTOSTIOMATA OP M()LC4ULA MANHATTENSIS. 147 



to form six rows of secondary braiicliial stigmata. I take the 

 latter vieAV, while recognising its arbitrary nature. 



The adolescent period would then be inaugurated bj the 

 change in the long axis of the secondary stigmata (cf. my 

 pi. xxxi, fig. 18, op. cit.), and characterised by the for- 

 mation, by subdivision from the secondary stigmata, of the 

 definitive or tertiary branchial stigmata ; and by the develop- 

 ment of the reproductive organs from the genital primor- 

 dium. 



It is satisfactory to note that collateral evidence in confir- 

 mation of the account which I gave (1) as to the increase in 

 the number of stigmata in a transverse row, and (2) as to the 

 increase in the number of transverse rows in Ciona, has been 

 forthcoming on the part of M. de Selys Longchamps ^ in 

 respect of Ascidiella scabroides: — "La regie generale est 

 la memo ici que chez Ciona intestinal is; tout nouveau 

 stigmate d'une rangeo n'est autre chose qu'une 

 partie separee d un stigmate preexistant." And 

 again : — " L'augmentation du nombre des rangees trans- 

 versales de stigmates ne resulte pas de Tapparition de rangees 

 nouvelles ciitre les rangees prt'existantes, niais du dedouble- 

 ment de ces rangees preexistantes, ainsi (pu' Willey I'a decrit 

 et re])resente fig. 22, chez Ciona." 



The formation of the intercahiry stigmata in a transverse 

 row of Ascidiella scabroides as described by do Selys 

 Longchamps ditt'ers in detail from the method Avhich prevails 

 in Ciona in that minute diverticula are budded off from the 

 ends of the pre-existing stigmata in a manner which strikingly 



recalls the mode of origin of protostigmata II and III in 



C( • t) 



;iona.~ 



Observations on Molgula manhattensis. 



My observations on Molgula manhattensis were made 

 during the long vacation of 1893, in the Marine Biological 

 Laboratory at Woods Holl, Mass., where I Avas privileged to 



' Op. cit., pp. l-2i— 126. 

 De Selys Loiigcliamps, op. cif., nl. viii, figs. 5 — 7. 



