[73] 



NOTES ON ENTOZOA OF MARINE FISHES. 



791 



ments become decidedly moniliforin posteriorly, each proglottis becomes 

 compressed anteriorly until it is reduced to a mere neck. It is also 

 compressed, but not so much, posteriorly. The margins are therefore 

 strongly convex. There is a tendency also on the part of some of the 

 posterior segments to assume an arcuate form, in which one of the lat- 

 eral faces is convex and the opposite one concave. Most of the alco- 

 holic specimens are somewhat fusiform, and the last segment is elon- 

 gated and compressed posteriorly as though the strobile had not yet 

 lost any segments. 



While examining the living specimens of the large lot I was for a 

 time disposed to think that there were two species, or at least two vari- 

 eties. A few appeared to be destitute of auxiliary acetabula. The 

 heads were smaller and the bothria had thinner margins than was the 

 case in the majority of examples. When the specimens were placed in 

 alcohol, six out of the forty-eight individuals at once assumed a marked 

 difference in form. The heads became natter and thinner, somewhat 

 flaccid, truncate in front, and wedge-shaped ; the necks were much at- 

 tenuated, even filiform, while the posterior end of the strobile was more 

 decidedly moniliform than in the normal type. This difference, while 

 quite striking, is, I think, due simply to difference in age and condi- 

 tions of contraction. It is to be noted that most of the individuals with 

 the slender necks are considerably longer than the others and have a 

 much larger proportion of mature segments. In the one or two whose 

 length does not exceed the average of the normal type, there is an ap- 

 pearance of general flaccidity as though the individuals were imper- 

 fectly developed. The difference between the two sorts with respect to 

 the bothria is probably due to a deterioration on the part of the smaller 

 lot, a conclusion which is further strengthened by the general appear- 

 ance of maturity of the strobiles. 



In the following table of measurements, Nos. 1 and 2 belong to the 

 smaller lot," that is, those with the attenuated necks, Nos. 3 to G to the 

 larger lot, or normal type. All the measurements are of alcoholic spec- 

 imens : 



Dimensions. 



Length 4 



Breadth of head 



Thickness of head 



Diameter of neck near head, lateral 



Diameter of neck at narrowest point... 



Distance to first segment 



Length of first segment (approximate) 



Breadth of first segment 



Greatest breadth of body 



Lengih of last segment 



Breadth of last segment 



No.l. 



HUH. 



No. 2. 



mm. 



No. 3. 

 mm. 



No. 4. 



No. 5. 



mm. 



mm. 



76.00 



45.00 



30.00 



46.00 



46. 00 



.90 



1.60 



1.48 



1.60 



1.40 



.36 



.50 



.60 



.00 



.70 



.28- 



.34 



.50 



.68 



.50 



.08 



.15 



.40 



.60 



.40 



14.00 



12. 00 



12.00 



10.00 



10.00 



.02 



.02 



02 



.02 



'.02 



1.00 



.90 



1.00 



.80 



.60 



1.00 



.94 



1.50 



1.06 



.80 



1.40 



1.30 



1.60 



1.30 



1.30 



.90 



.76 



.80 



.80 



.70 



No. 6. 



mm. 



28.00 



1.50 



.50 



.56 



.40 



10.00 



.02 



.80 



1.60 



.80 



.76 



