258 



MEAD. 



[Vol. XIII. 



glands, but does stain with Zocher's alum-cochineal. I do not 

 understand their structure and function; — possibly they are 

 homologous with the frontal bodies of Nereis (Wilson) (text 

 Figs. XII-XVIII). 



Cilia. — Cilia are seen first on the sixteen primary cells, and 

 then on all the twenty-five cells of the completed prototroch. 

 Next the paratroch becomes ciliated, and, at about the same 

 time, a tuft appears at the apical pole. The cilia of the proto- 

 troch and paratroch at first are very numerous and fine, and, 

 in each case, are distributed in an even zone encircling the 



Fig. XII. — Amphitrite, 28 hours, left side ; 

 gl.l., left dorsal umbrellar mucous gland 

 (opening) ; gl., ventral umbrellar mucous 

 gland; fl., flagellum ; muc, subumbrellar 

 mucous gland ; v.c, ventral band of cilia ; 

 c/r., anal cirrus; prob., problematic bodies. 



Fig. XIII. — Amphitrite, 36 hours, 

 ventral ; prob. , problematic bodies ; 

 gl., ventral umbrellar mucous gland ; 

 op. , its external opening ; mice, sub- 

 umbrellar mucous gland ; par. , para- 

 troch; dr., anal cirrus. 



trochophore. Later they become much larger, strong, and so 

 tough that they are often fairly well preserved with so harsh a 

 reagent as Perenyi's fluid. The apical tuft which is very large in 



