No. 3] LOXOSOMA DAVENPORT!. 35^ 



I mm. long. The stalk is terminated at its basal end by an 

 orbicular foot which has neither foot-gland nor lateral expan- 

 sions of any kind. Muscles having a spiral course are present 

 on the anterior side of the stalk connecting with the margins 

 of the foot. The number of tentacles most commonly observed 

 is between twenty-two and twenty-six. Buds are usually pres- 

 ent, varying in number from two to twelve. A single row of 

 large, prominent cells is present in the mid-dorsal line of the 

 body-wall. A pair of organs not mentioned as occurring in 

 any other species, and which will be described as flask organs, 

 are frequently present attached to the anterior wall of the 

 body, nearly opposite the oesophageal end of the stomach. A 

 modification of the floor of the atrium between epistome and 

 rectum will be described as a mammary organ. To this the 

 developing embryos attach themselves, and from it they 

 derive their nourishment. The anus opens in the center of 

 the lophophore upon a small papilla or anal cone, the posterior 

 wall of the rectum being attached throughout its length to the 

 lophophore. Dorsal sense organs do not occur in this species. 

 The Body- Wall ajid its Modifications. — The body-wall is 

 formed of a single layer of flattened epithelial cells, outside of 

 which is a thin, structureless cuticula 1-2 /a thick. The cells 

 forming the inner wall of the lophophore are somewhat more 

 attenuated than those upon its outer side. The tentacles which 

 arise from the margin of the lophophore have the epithelium on 

 their inner faces covered by long cilia, such as also line the 

 atrial groove at their bases. The only other portion of the 

 superficial epithelium which bears cilia is the oral face of 

 the epistome (PI. XXXII, Figs, i, 7, 9, 10). The tentacles 

 vary in number from about sixteen or eighteen, in the young 

 individual just separated from the parent, to twenty-six or 

 twenty-seven in the fully developed adult. The numbers most 

 commonly observed are from twenty-two to twenty-six. No 

 species has been described heretofore as having more than 

 eighteen tentacles. New tentacles arise alternately upon 

 either side of the median plane at the distal portion of the 

 lophophore, as shown by the frequent occurrence of one or two 

 immature tentacles in that position (Fig. i). When two are 



