PROTOSTIGMATA OF MOLGULA MANHATTENSIS. 141 



On the Protostigmata ofMolgula manhat- 

 tensis (De Kay).^ 



By 



Arthur ^Villey. 



With Plate 9. 



Introdcctiox. 



In the case of several species of simple Ascidians with 

 relatively alecithal eggs^ it is known that the larva^ at or 

 about the time of fixation, possesses two pairs of gill-clefts or 

 primary branchial stigmata. The period during which the 

 stigmatic system of the young Ascidian is represented by 

 these two pairs of clefts alone may be one of considerable 

 duration, thus constituting a definite stage of develop- 

 ment. This is succeeded by another w^ell-marked stage, 

 characterised by the presence not of three but of four stig- 



1 Molffula manhatt ensis is one of the comnioiiest Ascidians on the 

 coast of New England. Whereas other Ascidians are eclectic iu iheir dis- 

 tribution, this species, as Veriill and Sniilh ('lleport upon the Invertebrate 

 Animals of Vineyard Sound,' Washington, 1874) have shown, is at home in 

 all kinds of jjlaces. In Nev? Bedford it occurs or occurred in large clusters 

 on the piles of a wharf. I sent specimens to Professor Herdnian, who has kindly 

 informed me that he is satisfied that they are true Molgula. The species is 

 iheMolgula manhattensis of American authors, and the generic name 

 Bostrichobranchus, given to it by Tiaustedt, must rest upon some mis- 

 understanding which ought to be cleared up. Professor Herdman suggests 

 (in lit.) that the specific name manhattensis may be misapplied. It may 

 be so, but I think the burden of proof rests upon the author of the genus 

 Bostrichobranchus. 



There should be no doubt concerning such a common and easily obtainable 

 Ascidian. 



