The Anatomy of L,aila Cockerelli 



MABEL GUERNSEY 



In a recent number of this Jouenai, the circulatory system of this species was 

 described. The present paper is a continuation of that anatomical study. 



In cross-sections of the animal, the liody-wall may be seen 

 to consist of an outer layer of epitheliimi; within that a thick 

 layer of rather sponjyy connective tissite, containins- spicules, 

 blood spaces, and in places gland cells ; and within that again a 

 tliin layer of muscle lining the l)ody cavity. The connective 

 tissue and muscle stain with picro-fuchsin in a manner similar 

 to mamalian muscle and connective tissue, the muscle fibres 

 staining yellowish-brown and the connective tissue pink or red- 

 dish. The epithelium is very thin, consisting of a single layer of 

 short columnar cells, containing a few mucus cells. Over the 

 foot, however, it al)ru]itly changes its character and the cells 

 become much elongated and very strongly ciliated, except at the 

 anterior margin of the foot, where they lose most of their cilia 

 and assume the appearance of gland cells. The connective tissue 

 layer is most dense over the back and becomes very loose and 

 spongy in the foot, which contains a mass of blood sinuses. It 

 contains numerous spicules in tlie back, a few at the sides, and 

 a very few in the foot. These are irregular in shape and size, 

 but usually large at the center and tapering toward the ends, 

 with a small angle at the center. Sometimes there is a short 

 branch springing off near the center or they are more sharply 

 angled. Around the spicules, the connective tissue is condensed 

 to form a capsule. In the foot the connective tissue contains 

 masses of gland cells, grouped just below the epithelium. Over 

 the main part of the foot these masses are rather scattered and 

 small, but at the anterior angle they abruptly become very 

 numerous and closely packed and the separate cells become 

 larger. Here also, as has been said, the epithelium changes, 

 losing most of its cilia and resembling the gland cells in staining 

 reaction. The muscular layer consists partly of a distinct laj^er 

 lining the body cavity and partly of strands of muscles extending 



