Two New Tromatodes of the Family Gyrodactylidœ. 25 



a hoop (tig. 13); the length of a hook is 96/e for the larger one 

 and 84-89// for the smaller. The transverse connecting piece for 

 the ventral hooks is curved and short dumb-bell shaped and 19/* 

 long; that for the dorsal hooks is more slender and longer, being 

 26/* long. Under certain conditions these connecting pieces stain 

 very well. The hooks - are provided with retractors and pro- 

 tractors. 



The dermal musculature consists of the usual three layers, the 

 circular, diagonal and longitudinal. Dorsoventral fibres are also 

 present. 



The mouth opens on the ventral side at a short distance from 

 the front end of the body; its cavity extends backwards on the 

 ventral side of the pharynx to the hind end of the latter, while on 

 the dorsal side it extends less backwards; this condition is 

 however subject to alteration by the action of the retractor muscles 

 of the pharynx. The latter is wellnigh cylindrical in form and 

 when viewed dorsoventrally sends out two lateral horns back- 

 wards; it is surrounded on all sides by a distinct membrane of 

 •connective tissue and its main mass is formed by the radial muscle 

 fibres, in the large interstices of which lie the pharyngeal glands. 

 The circular and meridional fibres appear to be very weakly 

 developed. As viewed under the pressure of a cover glass, the 

 pharynx is 132/* long and 96/t wide. It leads into a very short 

 ■ossojjhagus, into which open numerous unicellular salivary glands, 

 the cells of which are located in the lateral parts of the body, 

 •outside the initial portion of the intestinal cceca. The cells are 

 pyriform and provided each with a long duct, which opens into 

 the oesophageal cavity; they may measure as much as 1'2/j. by 

 17//, and the cytoplasm lias hardly any affinity for borax carmin 

 but stains well with haematoxylin. The two intestinal cosca run 

 backwards on either side of the body and unite directly behind 

 the testis but again separate a little further backwards and termin- 

 ate blindly shortly afterwards. Each intestinal cœcum is provi- 

 ded on its outer side with short, secondary cceca, some 15-20 in 

 number, terminating near the body margin. Both the primary 

 and secondary cceca are lined with a tolerably thick epithelium, 



