ON THE DIPLOCHORDA. 287 



In 1867 Actinotrooha again came under detailed notice, 

 this time at the hands of Kowalevski (12), who gave an 

 account of the developmental changes and metamorphosis. 

 He identified the adult worm with Phoronis (syn. Crepina, 

 van Beneden). Written in Russian, this memoir would be a 

 sealed book to most morphologists were it not for a German 

 epitome. Yet again, in 1871, E. Metschnikoff (14) obtained 

 a number of early stages from the Mediterranean Sea, which 

 he described and figured, and also gave further particulars upon 

 the metamorphosis. Like his predecessors, he did not adopt 

 the method of sections in his work, or it is probable that some 

 further important facts on the structure of his young stages 

 would be to hand. After a period of some ten years the 

 Actinotrocha of Chesapeake Bay was investigated by E. 

 Wilson (22), who discriminated two species, and followed 

 out the metamorphosis. Disagreeing in minor points with 

 Metschnikoff, he confirmed in the main this naturalist^s 

 account. A large part of his paper is devoted to a discussion 

 of the significance of the metamorphosis and of the systematic 

 position of Phoronis. 



In 1883 a preliminary note upon the development of 

 Phoronis, besides other points, was issued by Caldwell (2). 

 So far as I am aware, nothing further has been contri- 

 buted by this worker except a short paper (3) on the early 

 stages of the embryos, although no doubt the expectation 

 of further contributions has caused the investigation of 

 Actinotrocha and its earlier stages to be neglected for the 

 last dozen years or so. In comparing my results with those 

 of Caldwell there has been an important difficulty to contend 

 with. In these days of rush for priority it is questionable 

 how far a worker can be expected to stand by every assertion 

 made in a '' preliminary " note, and it is also difficult in a 

 paper of this kind to discern how much of the statements 

 therein contained are claimed as original. If CaldweH's 

 paper does not, therefore, receive as much recognition below as 

 it would seem to be entitled to, its preliminary and therefore 

 tentative nature must be given as the reason and excuse. 



VOL. 40, PART 2. — NEW SEE. X 



