86 Notes on the Ascidea Mmihattensis, De Kay, 



by the nervons ring, composed of light-yellow cells, correspond- 

 ing nearly in size and color with the cells of the nervous gang- 

 lion of the Molgula Manliattensis. 



The body, enclosed Mdthin its own membrane already men- 

 tioned, lying nearest the apex opposite the orifice, now claimed 

 my special attention. When I examined it under the micro- 

 scope, after rupturing its membrane by means of the compres- 

 sorium of Purkinje, I discovered a body resembling an embryo 

 (Fig, 4). After a few days it had changed its form ; it was globu- 

 lar, with its tail partially surrounding the body, which, as soon as 

 I had loosened it from the body with insect needles, made occa- 

 sional sudden motions. No sexual organs existed at that time 

 in the Marmnaria in question. It was certain now that tlie 

 Mamvmaria was a nurse. 



I then examined many specimens, and found in each, as was 

 to be expected, one larva within its chorion. In regard to the 

 development of these larvae, I shall make at present but a few 

 statements, as it has been studied and accurately described 

 by Milne Edwards, Kolliker, A. Krohn, and others. The 

 younger larvae had three, those more developed two appendages, 

 those full grown three (?). These were conical at first, then 

 became triangular in form, perforated from the middle of the 

 base to its apex by a fine tubular canal ; those fully developed 

 had three appendages perforated by asmall tubular canal, divided 

 in its middle trichotomically (Fig. 5, «, 5, c). It is a fact worthy 

 of note, that the larvae escape from their nurses about the same 

 time, consequently in great numbers ; for I found them to a 

 certain day, but could not find any on the next following day, 

 though I examined a great number of Mammarim. It is in 

 favor of the supposition that the larvae of at least some simple 

 Ascidians, as well as those of the Salpae and of the compound 

 Ascidians, form as such colonies floating in the sea during a time 

 of their existence. An observation of Th. H. Huxley,* respect- 

 ing a marsupial Cynthia, that " the originally free-tailed larvae 



* Report of the Brit. Ass. for the Adv. of Sc, 1853, p. 76. 



