The Sunfish as a Host. 87 



to twenty inches in length, but they were imperfect individuals. 

 On a previous occasion, from the liver of a full-grown Ortha- 

 goriscus — for the opportunity of examining which we were 

 indebted to Professor Goodsir — we obtained several examples 

 fully double this length. Even these were incomplete speci- 

 mens ; and it is impossible to calculate accurately the length 

 any given worm may attain, because they are usually rolled 

 together in inextricable confusion ; moreover, the sheaths are 

 much longer than the worms themselves, being, as it were, left 

 behind in the tissues of the ' { host" wherever the parasites may 

 have wandered. There are thus found permanent indications 

 of the erratic movements of the "guests," and were it possible 

 in an adult sunfish to unravel the entire sheath of a single 

 Tetrarhynchus reptans, we should probably find the capsule — 

 representing, be it remembered, the entire life-wanderings of 

 the tapeworm thus far — at least one hundred feet long. In this 

 case, of course, we assume the worm to have entered the fish 

 while the latter was quite young. Whatever reflections such 

 phenomena are calculated to excite, one certainly sees no 

 reason to envy the piscine " host" thus destined to have its 

 muscles and viscera tunnelled in all directions by an uninvited 

 Tetrarhynch. 



Several questions here naturally suggest themselves, such 

 as : — What is the object of this perpetual tunnelling ? Does 

 the boring really cause suffering to the host ? Do the parasites 

 ever make their escape from the body of the fish ? To some of 

 these queries we believe ourselves capable of giving a satisfac- 

 tory answer ; but before doing so, it is necessary that we should 

 complete our account of the organization of this worm. In 

 this view, therefore, we have to remark that fig. 2 is a slightly 

 enlarged, but otherwise exact, copy of the upper end of the 

 Tetrarhynchus enclosed within its transparent capsule. The 

 rounded extremity is not merely the so-called head, but it em- 

 braces also the neck and its subcervical enlargement — all these 

 three distinct parts being represented in their unfolded condi- 

 tion in fig. 3. In the latter drawing, the numeral is placed 

 opposite the constricted portion of the hour-glass-shaped neck. 

 Immediately below this enlargement is a still more attenuated 

 portion corresponding with the narrow neck-like constriction 

 shown in fig. 2. The swellings below this, again, are identical 

 in the two figures, but in the lower illustration the body of the 

 worm is more drawn out. The so-called head in fig. 3 dis- 

 plays four proboscidiform tentacula — hence the generic title 

 employed — and also four cephalic lobes, each of which is fur- 

 nished with a sucking disk. In fig. 9, at the bottom of the 

 plate, we have given an enlarged view of this so-called head, 

 seen from above. The four proboscides are retracted within 



