237 
Dourn') in 1884 refers to a thymus in Petromyzon, but 
later BEARD?) has failed to find such in either the adult lamprey, 
or AMmocoetes, or very young larval forms. In the same paper 
BEARD (p. 485) states that the only positive statement on the thymus 
of Petromyzon is that which emanates from Srannius. “There 
can be no doubt’, he continues, “to my mind that the structure here 
referred to is the degenerate pronephros, for it is exactly in this 
position that one finds this body in Myxine’). 
Just as RATHKE’s views as to the homology of the modified head- 
kidney and suprarenal bodies crept into a number of the earlier text- 
books, so, brought forward again by WELDon, it has had a like career, 
thus WIEDERSHEIM suggests that a similar condition obtains in Teleosts. 
He writes*) (p. 353): “Bei Teleostiern sind die Nebennieren nicht 
überall in klarer und überzeugender Weise nachgewiesen; wo dies 
aber der Fall ist, handelt es sich, wie früher schon angedeutet wurde, 
um Beziehungen zu der in lymphoides (adenoides) Gewebe umge- 
wandelten Kopfniere. In anderen Fällen aber sind sie enge mit der 
Niere verbunden”, referring to a foot-note which runs as follows: 
“Dies gilt nach W. Wenpon auch für die Cyclostomen (Bdellostoma 
Forsteri)”. 
A paper on the head-kidney of Myxine by Miss KırkaLpy’°) 
gives a short description of MULLER’s gland, but, like WELDON she 
entirely overlooks the writings of the earlier workers, and falls into 
similar errors concerning its relation to the suprarenal bodies. 
JULIN 6) in 1886, in his careful researches, makes no mention of 
the bodies described by RATHkE, or any others which are analogous, 
which is somewhat to be wondered at. 
Morphological. 
The specimens we have examined are Myxine glutinosa, 
Petromyzon marinus, P. planeri and Ammocoetes. 
Examples of Bdellostoma we have been unable to obtain. 
1) Mitteil. a. d. Zool. Station zu Neapel, 1884. 
2) Anat. Anz., Bd. 9, 1894, p. 476—486. 
3) BEARD gives no reference to Stannius, but the only ones we know 
of are that quoted above (Handbuch d. Zoot.), and that in MüLLer’s Archiv, 
1850, p. 501—507, Taf. 15, in both of which he refers to MüLLEr’s 
clustered gland (= the pronephros) in Myxine. 
4) Lehrbuch d. vergleich. Anat, d. Wirbeltiere, 1886. 
5) Quart. Journ. Micr. Se., 1893—94, Vol. 35, p. 3553—359, Pl. 22. 
6) Archiv de biol., 1886, T. 7, p. 759—902, Pls, 21— 28. 
