35 



o 



difference: a "nerf buccal moven" and "externe" cannot be demonstrated. The cirrhi and 

 " Mundleisten" are directly innervated from the cerebral ganglion; the sublingual ganglia on 

 the contrary are clearly discernible (fig. 176). The commissures between the ganglion posterius 

 superius and the ganglia posteriora inferiora are distinct ; this is hoewever not the case 

 with the commissure between the ganglia posteriora inferiora, which is not visible in my 

 longitudinal sections. 



The animal is mature. The cloaca-ducts are of a simple structure. The part, passing out 

 of the pericardium proceeds first proximally as a straight, narrow ciliated tube, to bend after- 

 wards and to run distally. The cloaca-ducts coalesce; the precloacal organ is large and opens 

 into the cloaca. The part of the cloaca-ducts, running proximally, carries an appendage : a little 

 stalked vesicle (fig. 178) which may be compared with the vesicula seminalis of Stylomenia. 



Copulation-spicula and "organes en cordon" are absent. 



The cloaca is a small cavity, which is continued far distally into the pointed extremity 

 of the body. 



Regarcling the heart I cannot give any reliable data. From fig. 179 it is evident that 

 the heart is clivided into 2 parts (atrium and ventricler), but from the longitudinal sections 

 the exact structure cannot be made out. 



I believe that I have sufficiënt grounds for placing this form under Dondersia. Simroth 

 gives the following peculiarities for the genus Dondersia: "Gestreckt wurmförmig, cylindrisch; 

 Kopfende kolbig verdicht. Kloakenöftnung ventral. Schwanzende darüber fingerförmig. Fussrinne 

 biegt in die Kloake ein. Fuss vorhanden. Spicula nadel- oder schaufelförmig. Kiemen fehlen. 

 Radula vorhanden. Yentrale und dorsale Speicheldrüsen. Langen-index 10". 



With respect to this the following must be noticed. Dondersia festiva has not 4 but 

 2 salivary glands, the clorsal ones being absent. The latter are mentioned by Simroth because 

 Hubrecht makes mention of a gland, opening out into the pharynx and dividing into two 

 more proximally (3 fig. 9 k). On looking very closely at fig. 9 of Huisrecht we may observe 

 however that the said gland is nothing but the mouth-cavity with the cirrhi and "Mundleisten"; 

 Hubrecht's sections, which were thoroughly examined by me, do not leave the slightest doubt 

 on this point. The glands k' are present but must be regarded as accumulations of unicellular 

 crlands, also met with around the mouth.cavitv elsewhere ; of salivarv edands there can be 110 

 question here. From this it follows that also in Dondersia festiva the mouth-opening and opening 

 of the pharynx are separated from each other (cf. Hubrecht's fig. 9 and my figure 175). But 

 the ventral salivary glands of Dondersia festiva are structured like those of Dondersia annulata 

 and take a similar course. The radula of Dondersia festiva is monoserial and consists of (4?) 

 conical teeth behind each other. The structure of the pharynx and intestine is for both torms 

 exactly alike. The structure of the cloaca-ducts may also be compared : the vesiculae seminales 

 of Dondersia annulata may be compared with the tubes / and /' of Dondersia festiva (3 fig. 3); 

 the stalked vesicles A of Dondersia festiva however are absent here. The byssus-gland of 

 Dondersia festiva is not present here, but in my opinion this gland should be differently inter- 

 preted, being simply a proximal offset of the cloaca. The spicula of both forms are very much 

 alike. The finger-shaped projection of Dondersia festiva is not found here, but an indication of 



