PK0T0STIG3JATA OF MOLGUf.A ]\IANHATTENS1S. 149 



same time three or four liolloAv ectodermic processes grow out 

 at different points from the main body, and project into the 

 test (cf. PI. 9, fig. 3). These processes are contractile, and 

 their somewhat dilated extremities may sometimes be seen to 

 execute a prominent systole ; they are still to be seen at the 

 end of the nepionic 2Deriod (fig. 12). 



Under certain imperfectly known circumstances the larva 

 may undergo a portion of its metamorphosis while still en- 

 closed within the follicle, so that it passes through no free- 

 swimming stage. ^ 



I am quite unable to say whether such precocious metamor- 

 phosis is a normal variant, but even if it is a teratological 

 phenomenon it is of some interest, and would have a more 

 definite significance if (1) the exact circumstances under 

 which it takes place were determined, and (2) it were ascer- 

 tained whether any of the individuals attained maturity. 



In fig. 2 a larva is shown whose tail is in regression 

 within the follicle. One point of special interest in this 

 larva is the great development of the praeoral lobe (organ of 

 fixation), which extends as a hollow tube containing loose 

 mesenchyme, close ])eneath the follicular membrane between 

 the latter and the eml)ryo. In this position it appears likely 

 that it would fiiKil a i-espiratory function, since I observed it 

 to contract and expand. In the same larva (fig. 2) there 

 were two round pigmented bodies in the larval brain. Often 

 only one spot is present ; one only was observed by Kingsley 

 in this species, and one by Julin in Lithonephria. I found 

 reason for supposing that the presence of two spots might be 

 due to the fragmentation of a single one. What has been 



1 This indication of precocious mclanior|iliosis is of iinpoitance in com- 

 parison witli the development, of other Molgulids, in which, according to the 

 observations of Lacaze-Duthiers and Kupffer, the urodele stage is omitted 

 from the ontogeny. It also recalls to my mind some experiments which I 

 made on species of Styelidse some years ago, when I succeeded in hastening 

 the preliminary stages of the metamorphosis by cutting ofT the tails of the 

 larvse. [A. Willey, "Report on the Occupation of the Table of the British 

 Association at, the Marine Biological Laboratory, Plymouth, during August 

 and September, 1891," ' Rep. Biit. Ass. (Edinburgh),' 1892.] 



