[55] NOTES ON ENTOZOA OP MARINE FISHES. 773 



Length, 25.55 ; length of bothrium at rest, .7 ; breadth, .53 ; breadth 

 of head, 1.23; breadth of first segments, about 1 back of head, 4 ; length, 

 03; breadth of median segments, .72; length, .15; average length of 

 posterior segments, .13; breadth, .8. 



In the above specimeu there was a constriction behind the head .2S mm 

 in diameter, while immediately behind the constriction the neck was 

 .46 mm in diameter. Near the posterior end of the strobile there was an 

 enlargement due to contraction, which was l.l m,M in diameter. In an- 

 other specimen, 20 mm in length, the first segment began less than l mm 

 from the head, where they were .8" ,m broad and ,05 mm long. The median 

 segments were 1.4 ,mu broad and .l mm long. The posterior segments 

 were narrower, breadth, .44 mm , length, .4G" U ", with rounded angles, 

 the strobile here being somewhat moniliform. 



The vessels of the water- vascular system were quite evident in the 

 living specimens, both in the body and the bothria. One set of longi- 

 tudinal vessels, consisting of a single vessel near each margin, was pe- 

 culiar in that each vessel was quite irregular, swelling out into suboval 

 enlargements and giving off short lateral branches at intervals. These 

 may be nervous vessels. 



When the specimens were placed in alcohol the longest of the three 

 contracted until it was shorter than the others. 



Anatomy of the segments and bothria. — A few of the posterior segments 

 of one specimen were stained with carmine and cut into longitudinal sec- 

 tions. The segments all proved to be immature, and consequently only 

 a comparatively few points in their anatomy could be made out. 



The outer coat of the muscular wall is composed of two layers of 

 finely fibrous tissue, an outer layer of circular, and an inner of longitu- 

 dinal fibers. In sections these two sorts cross each other at right an- 

 gles, forming a net- work with rectangular meshes. Beneath the outer 

 fibrous layers is a thick layer of densely granular tissue. The granules 

 stain deeply with carmine, and are from .003 to .006 I,,m in diameter. 

 Beneath the granular layer is a layer of longitudinal muscle fibers. 

 These are larger than the fibers in the outer longitudinal layer, and 

 are arranged in straight, parallel fascicles, which are from .0025 to 

 .005 mm broad and .0025 miu apart. 



The most prominent organ in these segments is the cirrus and its 

 sheath. In all cases the former was retracted. The external opening 

 of the cirrus is at the margin near the anterior edge of the segment. 

 The sheath, with the inverted cirrus, extends a little past the middle 

 line of the segment. The cirrus when extruded must be therefore rela- 

 tively quite long. The sheath enlarges towards the center of the seg- 

 ment, where its diameter nearly equals the length of the segment. 

 The length of one was ,28 mm ; its diameter at base .027" ,m . The cirrus 

 throughout all its length is thickly beset with spines. The spines at 

 the base are much longer and stouter than those along the middle and 

 at the apex. Some of the basal spines were .008 mm in length, and .003 mm 



