
Haswett—A Monograph of the Temnocephalee. 95 
A. Vayssiere* describes a new form found on the surface of the Madagascar fresh-water 
crayfish. 
This remarkable group now proves to be of comparatively wide distribution, and 
to inhabit the surface of a considerable variety of animals. It has now been found in 
Chili, Brazil, New Zealand, Australia, Tasmania, Borneo, Celebes, the Philippines, 
Madagascar, and perhaps India. The various species infest the outer surface, and in 
one or two cases the branchial chambers, of fresh-water Crustaceans (both J/acroura 
and Brachyura) and fresh-water Chelonians, and the branchial chamber of a Mollusc 
(Ampullaria ). 
That the position of Zemmnocephala in the system is not to be regarded as a 
settled one is evidenced by the view of the matter taken by Braun in the general 
work on the ectoparasitic Trematodes above referred to. He says (Zc. p. 520), 
“Temnocephala bietet allerdings eine Reihe von Besonderkeiten dar und die Frage 
ist trotz der Arbeiten von Haswell und Weber gerechtfertigt, ob Temnocephala ein 
Trematode ist.” Further on (p. 521), after quoting von Graff’s definition of the 
Turbellaria, he remarks, “Wenn man von der letzten Bemerkung iiber die Lebens- 
weise, die keinen systematischen Werth besitzt, absieht, so bleibt als einziger 
Unterschied zwischen Turbellarien und Trematoden das fiir erstere characteristische 
Flimmerepithel der Haut mit Stiibchen oder Nesselorganen bestehen.” 
My renewed study of Tesnocephala having resulted in the discovery of cilia on 
the surface of certain of the species, and having led to the conclusion that ‘“Stibchen” 
exactly like those of Rhabdoccele Turbellarians are present in abundance, the line of 
demarcation seems still harder to draw. Zemmnocephala has no near allies in either 
camp; but in some features of its organisation it nearly resembles some of the 
Monogenetic Trematodes, while in others the connection with some of the Rhabdocwla 
is extremely close. With the evidence now before me, it appears to me that the 
Temnocephalee, though it cannot be said that they seem to lie in a direct line between 
the two groups, yet unite in such an equal degree the characters of the Monogenetic 
Trematodes and Rhabdoccela that they may almost indifferently be ranked with 
either. This question is discussed more fully in the sequel. 
II.—GeneraL Exrrernan CHARACTERISTICS. 
Monticelli’s and Braun’s comparison of Zemnocephala to a minute Cephalopod is 
very happy. The light-coloured, more slender kinds, such as 7. wzxor, are, when 
* “Etude sur le Temnocephala, parasite de l’Astacoides Madagascariensis.” ‘Annales de la Faculté des Sciences dle 
Marseille,’ Tome II. fase. v. (1892). 
