456 



anus seems to arise subsequently, at the posterior extremity of the 

 embryo. During the segmentation periods of activity alternate with 

 well marked periods of rest. 



The larva acquires dorsal eye-specks, a very broad prae-oral belt of 

 short cilia, a much narrower prae-anal belt and a broad ventral band, 

 and then passes directly into the adult, without decided metamorphosis. 

 The setae develop from before backwards, and those of the dorsal ra- 

 mus appear before those of the ventral. 



2) Aretiicola cristata Stimpson, The eggs of this huge annelide 

 are, like those of Chjmenella. embedded in gelatinous masses. These 

 masses are from two to six feet in length, from six to two inches in 

 diamètre, and each contains several hundred thousand eggs. The pro- 

 toplasm is slightly brownish in color so that the masses appear of a de- 

 cided cinnamon-brown color. The eggs are much smaller than those 

 of Clymenella^ and are more nearly spherical. The e^g membrane is 

 proportionally much thicker and is strongly striated radially when viewed 

 by oblique light. The segmentation and subsequent development are 

 almost identical Avith those of Clymenella and the same account will 

 serve for both. The embryos are likewise Telotrochous forms but the 

 cilia of both the anterior and posterior belts are much more powerful and 

 the larvae swim more rapidly and freely. The period during which the 

 young of both species swim freely at the surface is very brief. Both soon 

 sink to the bottom and secrete tubes or gelatinous masses in w^hich they live. 



3) Diopatra cuprea (Claparède) . The eggs of this species are still 

 larger than those of Clymenella and are likewise embedded in gelati- 

 nous masses attached to the mouths of the tubes of the worms. They 

 are nearly spherical, perfectly opaque, and are pigmented in irregular 

 spots on the surface. The masses are cylindrical, 18 inches to two feet 

 in length and about i/o ^^ch in diamètre. The jelly is very soft and 

 slimy. Of the early stages I can unfortunately say nothing. All efforts 

 to find the segmentary eggs were unavailing. The larvae are at first true 

 Atrocha, having an anterior apical tuft, a very broad band in the middle 

 region and a narrow and irregular anal band. Two reddish eye-speeks 

 are present and the larva closely resembles the Eunicid larva figured by 

 Claparède and Metschnikoff. The antennae bud out when the larva 

 has acquired 4 setigerous segments. The tentacular cirrhi appear later. 



4) Spiochaetopterus oculatus Webster. Larvae taken in Chesa- 

 peake Bay which are in all probability of this species are. like other 

 Chaetopterid larvae, mesotrochal. There is a single belt of cilia. The 

 larva is closely similar to that qî Phyllochaetopterus figured by Cla- 

 parède and Metschnikoff. The branchiae first appear when the 

 posterior region has about ten segments. 



Druck von Breitkopf und Härte) in Leipzig. 



