1901.] 



NATURAL SCIENCES OF PHILADELPHIA. 



673 



Inner Circular Muscle. 



Carinina grata, 



CarineUa— 



a. superba, 



b. annulata, 



CarineUa 



banyulensis, 



CarineUa 



rubicunda, 



CarineUa 



polymorpha, 



CarineUa 



Unearis, 



Structure. 



thicker in ne- 

 phridial region 



uniform 



ness 

 uniform 



ness 



lliick- 

 thick- 



thinner in ne- 

 phridial region 



thinner posterior 

 to uephridial 

 region 



thicker in ne- 

 phridial region, 

 very thin poste- 

 rior to nephri 

 dia 



thicker in ne 

 phridial region 

 thin posterior 

 to nephridia 



CaUinera thinner behind 



biirgeri Berg., | " rhynchoccel 

 muscle sack " 



Hubrechtia, 



Carinoma, 



luniformly thin 



great thickening 

 at nephridia 



Cephalot.hr ix aU- wery tliin, deli- 

 oia Punnett, i cate layer 



ZygeupoUa, 



Micrura, 



absent in oesopha- 

 geal region, ap 

 pears as a thin 

 layer about 

 mm. anterior to 

 middle intes 

 tine, very thick 

 at posterior end 



absent in resopha- 

 geal region, ap- 

 pears as a tliin 

 layer a short 

 distance in 

 front of the 

 middle intes- 

 tine.quite thick 

 at posterior end 



Extent. 



throughout body 



(?) 



throughout body 

 throughout body 



throughout body 



throughout body 



throughout body 



from the mouth 

 to nephridia, 

 and a short dis- 

 tance behind 

 them 



from the mouth 

 to close behind 

 the "rhyncho- 

 ccel muscle 

 sack" 



Crosses between 



Inner Circ. 



Muscle and Outer 



Circ. Muscle. 



Position 



of 

 Crosses. 



ventral cross only in region posteri- 

 or to nephridia 



dorsal and ven- throughout body 



tral 

 dorsal only throughout body 



dorsal cross only in uephridial re- 

 gion 



wanting 



dorsal cross faint, throughout body 

 ventral cross 

 wanting 



wanting 



wanting 



throughout body wanting 



(?) ' 



from mouth to dorsal and ven- from the mouth 



endof nephrid- 

 ial region 



(esophageal re- 

 gion only 



extends forward 

 for 2 mm. just 

 anterior to mid- 

 dle intestine 



tral 



(?) 



dorsal and ven- 

 tral 



extends forward! dorsal and ven 

 a short distance I tral 

 in frontof mid- 

 dle intestine 



to end of ue- 

 phridial region 



at posterior end 

 of the inner cir- 

 cular muscle 



at posterior end 

 of the inner cir- 

 j cular muscle 



The question now arises, can the so-called " oesophageal mus- 

 cle " (Darmmusculatur, Burger) be correlated in any way with 

 the inner circular muscle ? 

 43 



