[13] ENTOZOA OF MARINE FISHES OF NEW ENGLAND. 465 



The neck is continuous with the head, slightly flattened, and tapers 

 away from the head very gradually in fully grown specimens, so grad- 

 ually, that its progress cannot be noted, except by comparing the width 

 of the proglottides with that of the neck. The neck is marked with 

 longitudinal rugae, which continue well back on the forming proglot- 

 tides (Figs. 1, 2). Where the transverse strice, which mark the forming 

 proglottides, begin, the surface of the body presents a rough, checkered 

 appearance, due to these two systems of grooves, which is quite char- 

 acteristic, and may serve to identify a fragment of one of these worms 

 when neither head nor mature proglottis is present. 



Proglottides, before they become free, are much broader than long, 

 and each has a short, free posterior border, which becomes the rim or 

 border mentioned in the description of the free proglottis. Penis very 

 long, with a bulbous enlargement at the base. Near the posterior end 

 the segments become rounded at the corners and somewhat elongated, 

 until they graduate into the shape which is characteristic of the mature 

 free joints. 



Free proglottides (Figs. 4, 5) about twice as long as broad, very 

 changeable in form, but in general rounded anteriorly ; the extreme 

 anterior end prolonged into a contractile papilla, which acts somewhat 

 as a sucking-disk in aid of locomotion ; posterior end truncate, with a 

 narrow rim or border marked off from the basal edge by the transverse 

 water-vessel. Sexual apertures marginal, opening a little back of the 

 middle point. Penis very long; when erected, longer than the proglot- 

 tis. Vagina opening immediately in front of the penis, flaring slightly 

 at the mouth, quickly contracted into a short cylindrical tube, then ex- 

 panding, finally reduced to a narrow tube, which runs anteriorly along- 

 side a central clear space, enters the latter, and near its anterior end 

 turns sharply, and runs back along the middle of the clear space until 

 it unites with the ovaries in the posterior part of the proglottis. 



Good preparations of the mature proglottides were obtained by sub- 

 jecting them to slight pressure between two cover-glasses held in phice 

 by a spring wire-clip and hardened while in this position. When seg- 

 ments so prepared were afterwards stained, made transparent, and 

 mounted, they were free from wrinkles or distortions, and showed the 

 internal anatomy as well, indeed better, for topographical purposes, 

 than could be shown with thin sections. 



The chyle in the spiral intestine of the host, Tiger Shark (Galeocerdo 

 tigrinus), swarmed with free proglottides, which were quite active. They 

 had powers of independent movement and locomotion which gave them 

 much the appearance of Trematods. 



About twenty specimens in the strobile condition, but representing 

 three stages of development, together with great numbers of free prog- 

 lottides were found in the spiral intestine of a Tiger Shark ( G. tigrinus). 

 The larger adult specimens varied in length from one -half to one meter. 

 S. Mis. 90 30 



