structure of the ovary in Chimaericolidae should hardly be considered as a 

 secondary phenomenon because we also observe similar pictures among 

 Turbellaria. 



Without dwelling on a number of other peculiarities of the 

 anatomy of Chinnaericolidae we can say that as a whole this family pos- 

 sesses a number of very primitive peculiarities along with the very 

 advanced specialization which was clearly expressed. As we will see 

 further, this conclusion has important meaning for an understanding of 

 the correlations of the evolutionary ways of developnnent of the given group 

 (see page 449 ). 



3. Order Mazocraeidea Bychowsky, ord. nov. 

 Diclidophoroidea Price, 1936; Dactylocotyloidea Brinknnann, 



1942. 



Oligonchoinea, having larvae with 10 edge and 4 middle hooks 

 on the attaching disc. As an exception, the number of edge and middle 

 hooks can be smaller and also the clamps can appear at the place of one 

 pair of edge hooks in the embryonic period. The attaching armature of 

 the adult forms consists of more or less typical clamps numbering from 

 4 to several tens of pairs. Sometimes the nunnber of the clamps is smaller 

 and they develop only on one side of the disc. The larval armature partially 

 remains during the entire life, and the anterior edge hooks enter, changing 

 their shape, into the composition of the chitinous elements of the clamps 

 and in a number of cases disappear, predominantly by means of a casting 

 off of the posterior part of the disc and of the pair of edge hooks and two 

 pairs of middle hooks which are located in it. The cephalic end has three 

 more or less developed groups of glands. The buccal opening is ternainal 

 or subterminal. Its cavity is equipped with 2 muscular suckers, not 

 homologous to the cephalic suckers of Polyonchoinea. The eyes are absent 

 among adult forms; among larvae they are either absent or there is one 

 pair of eyes usually merged; more seldom there are 2 pairs. The digestive 

 system has a pharynx, usually a short esophagus and two intestinal trunks 

 terminating blindly or merging. As a rule the trunks of the intestine have 

 numerous lateral outgrowths which also anastomose with each other, in 

 connection with which the intestine often assumes a net-shape. Mostly 

 there is a common sex atrium often armed by various thorns. The armed 

 or unarmed copulatory organ opens into the atrium. The testes are more 

 or less numerous, more seldom there is one testis. The ovary is usually 

 strongly curved with a flask-shaped oogonial chamber. The vaginal ducts 

 are double or single, they open by one or two apertures often armed by 

 chitinous hooks. The uterus is strongly developed, it is often sac-shaped. 

 The vitellaria are strongly developed, they lie along the sides of the body. 



498 



