REPTILIAN TAPEWORMS. 249 



ovaty. These ingrowths of the vitelline tissue are limited to the 

 posterior region of the gland. Furthermore, the preparation 

 which is represented in the text-figure shov/s that the vitelline 

 gland is distinctly thicker posteriorly in the region of the ovary, 

 and that it tapers somewhat anteriorly. These apparently minute 

 facts are important when we consider the characteristics of the 

 vitelline glands among the Cestoidea. Among the Tetracotylea 

 ( = Cyclophyllidea), to which group Ichthyotcenia and its imme- 

 diate allies have been by some referred, the vitelline gland is 

 single and compact, and lies nearly always behind the ovary, 

 ?'. e. quite posterior in the segment, but always near to the ovary. 

 On the other hand, the Tetraphyllidea, to which Ichthyotcenia 

 and its allies are more generally referred, have strip-like vitelline 

 g]a,nds situated laterally. 



At first sight Ichthyota^niids appear to conform entirely with 

 the latter definition. It seems to me, however, that Solenotcenia 

 shows quite intermediate characters. The thinning of the 

 vitelline strip anteriorly, and the projections posteriorly directed 

 towards the middle line of the proglottid, if they were carried 

 farther — i. e. to the disappearance of the anterior part of the 

 glands a"nd the junction of the posterior regions — would pi-oduce 

 the vitelline gland characteristic of the Tetracotylea. Another 

 matter in reference to the vitelline glands remains for con- 

 sideration. Riggenbach *, in his account of the anatomy of 

 Ichthyotcenia abscisa, distinctly states that the vitelline strips lie 

 outside of the water-tubes and the nerve-coid, while Schwarz t 

 writes absolutely to the same effect of /. nattereri : " Die Dotter- 

 stocke liegen wie bei alien Ichthyotajnien ganz randstiindig, 

 ausserhalb der Nerven und der Langsgefiisse und reichen vom 

 vordern Gliedrande bis zum hintern." This obviously implies 

 their position in the cortical parenchyma. 



In defining the Tetraphyllidea, in which gi^oup he includes the 

 Ichthyotpeniidje as a family. Prof. Max Braun ± writes : " Dotter- 

 stocke in zwei seitlichen Feldern resp. in randstiindigen Liings- 

 treifen — in der Rindenschicht." This phrase seems to imply an 

 agreement with the opinions just quoted, i, e,, that the stiips of 

 vitelline follicles lie in the coi-tical layer outside the nei-ve-cord. 

 Nevertheless in a figure § (copied from Kraemer) it is distinctly 

 shown that in " Tcenicf, Jilicollis " (an Ichthyotcenict) the vitelline 

 strips lie within, not only the nerve-cord, but the water-vessel. 

 In Solenotcenico there is no doubt that the vitelline strijis lie to 

 the inside of the nerve-cord though outside of the water-vascular 

 tube, and are thus obviously medullary in position. They also 

 certainly lie within the nerve-cord in other Ichthyotseniids which 

 I have myself |1 had the opportunity of examining. 



* Rev. Suisse Zool. iv. 1897, p. 210. 



t " Die Iclitliyotfeiiien der Eeptilien," Inaxig.-Diss. Univ. Basel, 1908, p. 22. 



I Bvonn's ' Thien-eiclis,' Bd. iv. Abtb. 1 B, p. 1699. 



§ Loo. cit. Tiif. Iv. fig. 5. 



[| P. Z. S. 1913, p. 4. 



Proc. Zool. Soc— 1913, No. XVII. 17 



