The Microscope. 1.63 



It is consequently with great pleasure that I am able to figure for 

 the first time a beautiful Mitraria-like larva, which is found in 

 abundance in the cold waters of the Bay of Fundy. This larva does 

 not occur south of Cape Cod, although it is represented in the 

 waters of Massachusetts Bay, at Provincetown, Mass. It is different 

 in form from the European representative of which in truth, con- 

 sidering the part which it has played in discussion of the aflfinities 

 of larval forms of animals, too little is known. 



My new larvge was first taken by means of the drag-net or tow- 

 net, in the summer of 1886. I first found it at Frye's Island, New 

 Brunswick, and afterwards it was taken at Grand Manan. The 

 larva occured in countless multitudes in July, and later decreased in 

 numbers and was collected far into August. Later than August 

 however, I have never seen Mitraria in the nets, although it may and 

 probably does last long into the autumn. The following lines will 

 give an idea of the general contour and structure of the body of my 

 new larva. 



The body (PL I ) is hat-shaped, with a narrow rim, gelatinous 

 and transparent. When contracted the sequatorial rim or belt of 

 the worm is drawn to the body imparting a spherical form to the 

 animal. The contracted form of the larva is seen in Fig. Ill ; the 

 expanded in Figs. I and II.* 



There are two ciliated regions of the body. One of these is 

 situated at the apex of the larva, forming a small tuft of cilia shown 

 in the figs. I, II and III. The second ciliated region is found 

 on the rim of the larva, forming a belt, skirting the outer border. 

 This second region or ciliated belt is conspicuous on account of the 

 masses of reddish pigment shown in the figures. 



Hanging down from the pole of the larva, opposite the apical 

 tuft of cilia, there is a bifid protuberance from which arises two fan- 

 shaped bundles of provisional setae. These setse resemble embryonic 

 setae so common in larval chsetopods. They can be drawn together 

 or separated and are always very conspicuous. Above the protuber- 

 ances from which the spines arise, there is a spherical, darkly 

 pigmented body easily seen through the walls of the larva. ( Figs. 

 I, II and III.) 



Under the apex of the larva there is a thickening of the epiblast 

 which is connected with the marginal belt by means of a fine thread, 

 shown in figs. I, II and III. The apical tuft of cilia rises from 



* la the figure? of the plate accotnpanying'this paper, Fig. I is a view of the Mitraria- 

 like larva fro a one side. Fig. II. Tae same. Fi^. III. Lateral view of larva with the 

 marginal rim contracted. This is a common attitude assumed by tae larva when at rest. 

 Fig. IV. View of larva from lower pole. 



