674 



PROCEEDINGS OF THE ACADEMY OF 



[Dec, 



Burger (1895), p. 257, speaks of a musculature ("Darmmuscu- 

 latur") that is developed in the Meso-, Meta- and Heteroneraer- 

 teans around the posterior part of the esophagus, consisting of both 

 longitudinal and circular fibres, the fibres being more slender than 

 those of the body wall. 



On p. 237 the same writer says that the dorso-ventral fibres that 

 occur so frequently between the intestinal cseca, and also in the an- 

 terior part of the liody, may be regarded as parts of a formerly con- 

 tinuous inner circular muscle layer. " Wir konnen die dorsoven- 

 trale Musculatur als eine innere Kingmuskelschicht, welche in 

 lauter, in gewissen Abstilnden aufeinanderfolgende Ringe zerlegt 

 wurde, vorstellen." He adds that sections of Eupolia and Lmeus 

 geniculatus, the latter figured on Taf. 20, Fig. V, strengthen this 

 opinion. In L. geniculatus the dorso-ventral fibres have bent 

 around the intestine, on its dorsal as well as on its ventral face, 

 making a continuous ring of circular muscle, and a crossing be- 

 tween these fibres and the circular muscle of the body wall takes 

 place in the median ventral line. 



P S 



^CAf 



i C M 



I nt 



Diagram 3. — Cross section through the body of Ccrehratulus lacteus, 

 illustrating the deflection of the dorso-ventral muscle fibres into the inner 

 circular muscle layer around the intestine. — P.S., proboscis sheath ; o. CM., 

 outer circular muscle ; Int., intestine ; i. CM., inner circular muscle ; I)v.f., 

 dorso-ventral muscle fibres. 



From my own observations upon Cerehratulus lacteus, Lineus 

 lacteus and a Lineus sp. , all preparations kindly lent by Dr. Mont- 

 gomery, 1 find there is frequently quite a considerable layer of 

 circular muscle fibres beneath the intestine, and also on its dorsal 



