To the first group of anterior attaching structures are related 

 the head papillae, the bothria, the little pits and suckers. The second group 

 includes the buccal funnel, the pharyngeal sucker, and the buccal funnel 

 suckers. In this connection the anterior end of the most primitive mono- 

 genetic trematodes is sonnewhat flattened dorsoventrally , is rounded or p. 16 

 truncated, and the numerous ducts of the head glands open along its edge, 

 apparently heterogeneous, but actually producing an agglutinating secretion 

 which serves for the attachment for the anterior end of the body. In the 

 majority of cases, in the forms which have as yet no differential growth 

 of the anterior end of the body, the excretory ducts of the head glands are 

 not located evenly along the entire anterior edge, but by groups of from 

 8 to 2 clusters (Fig. 11). In connection with this, we observe in a series 

 of sections the formation of head organs the anterior end of which are in 

 the form of more or less well-developed but always moving lobes. The 

 The number of head glands is usually paired, from one (for instance 

 Gyrodactylus , Fig. 12) up to 4 (for instance Murraytrema, Fig. 13). One 

 often sees two pairs of head glands (for instance Dactylogyrinae , the p. 18 

 majority of Ancyrocephalinae and others--Fig, 5, 65 and others). Each 

 head organ receives at its posterior end ducts of the clusters of head glands. 

 As a rule, one cluster of ducts of head glands enters into one head papilla, 

 nevertheless sometinnes a great number also enter a single head papilla 

 depending upon an increasing size of the head papillae. The latter, in a 

 series of cases; develop unequally so that two of them gradually pre- p. 19 

 dominate and the others disappear (for instance Diplectanum , Fig. 14). 



Next in complexity of the anterior attaching apparatuses are 

 the attaching bothria. The latter have the appearance of two thickenings 

 of the body symmetrically located on the sides of the anterior end and are 

 weakly separated from it. The musculature of these head bothria is 

 stronger than that of the head papillae and the head glands open into them 

 with many individual ducts or by several clusters, (for example Emprutho- 

 trema, Fig. 15), or equally spaced along its full length ( Dionchus , Fig. 16). 

 It is absolutely clear that the head bothria represent the latest stage of 

 morphological development of the head organs. Further, the process of 

 complication involves increased musculature of head bothria, and its sepa- 

 ration from the musculature of the body and the appearance of cup-like in- 

 dentations on the external side of the bothria, which leads at first to the 

 formation of head pits (for instance Nitzschia, Fig, 17), and also, during 

 the following development (both in the phylogenesis and ontogenesis) leads 

 to the forination of more or less strongly developed head suckers (for 

 instance Tristoma, Fig. 4). As a rule there is one pair of head bothria 

 or suckers (the following present exceptions: 1. The genera Bothitrema , 

 the only species of which R. bothi (MacCallum) (Fig. 19) has, judging by 

 the drawing and description of Price (Price, 1937b), four adhesive pits p. 20 



on each side of the anterior end (see however page 396); and secondly, 

 the genera Loimos and Loimosina (Fig. 20) in which the anterior end has 

 four small head suckers. As for the head glands in adult forms, the 



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