Contributions to the Anatomy and Histology of Thalassema neptuni Gaertner. 551 



Echiuroids, at any rate it occurs in JEchiurus (Spengel). Bonellia 

 (Rietsch), Hamingia (Hoest) and in representatives of the two great 

 divisions of the genus Thalassema viz Th. neptuni (Rietsch) and 

 Th. erythrogr amnion (Sluiter, 14). The intestine of Thalassema neptuni 

 may be divided into three parts, histologically scarcely distinguish- 

 able: the anterior (Zwischendarm, Spengel, 17) running from the 

 pre-intestinal constriction to the origin of the collateral intestine, 

 measuring 7 — 10 mm in length (Fig. 12 between p and ci); the 

 second (Mitteldarra und Nebendarm of Spengel, division b of Rietsch) 

 extending from the origin to the end of the collateral intestine (Fig. 1 1 

 c.i.o to c.î'.e), and the third (Hinterdarm, Spengel) accompanied 

 throughout its course by the ciliated groove and ending at a little pouch 

 or coecum (Fig. 11 coe) which marks the beginning of the rectum. 



From the pre-intestinal constriction backwards the intestine 

 usually contains a number of very characteristic ovate food-balls. 

 They often occur in immense numbers at certain spots (Fig. 11, the 

 loop before c. ie), and in such cases the intestine is dilated to many 

 times its usual diameter, its walls being stretched to the condition of a 

 thin transparent membrane. Isolated food-balls occur in the "Z wi s c h e n- 

 d a r m" and "M i 1 1 e 1 d a r m", but it is generally further back that they 

 are found in such great numbers, and form these conspicuous groups. I 

 examined some of these balls and found them to consist of aggregates 

 of sand and dark amorphous matter, which I regard as organic debris ; 

 also fragments of sponge spicules, Foraminiferan shells, parts of the 

 calcareous skeleton of Echinoderms, etc. 



In three carefully measured examples the parts under consideration 

 were as follows; 



.... region bearing hinder division from 



iirst division n . , • . i.- . ■ . c 



r, . , J collateral intestine posterior end of 



= Z wische udarm ,,... , , kt u a 



=- Mitteldarm Nebendarm to coecum 



small example, Plymouth, alcohol 7 mm 



full grown example, Valentia, formol 10 ,, 



The relative lengths of these parts is, no doubt, greatly influenced, 

 particularly in preserved examples, by the degree of contraction and 

 the number of sand balls contained, so that measurements from pre- 

 served material are not exactly reliable. 



I cannot find any regularity in the arrangement of the individual 

 loops of the intestine, except that a loop always runs forward from 

 the rectum on the left side and returns upon itself. The remaining 

 parts are less regular, and generally form a confused system of coils 



Zciol. Jal,rb. XII. Abth. f. Mcrph. g(j 



