1891.] TADPOLES OF THE EUROPEAN BATRACHIANS. 597 



(Actes Soc. Linn. Bord. xxxi. 1876, p. 95, and Rev. Intern. Sc. ii. 

 1878, p. 488) belongs the credit of realizing its full systematic 

 importance. We are indebted to Goette (Eutwick. d. Unke, p. 6/6, 

 pl.xviii., 1875) and to Heron Royer (Bull. Soc. Zool. France, 1887, 

 p. 645), who watched the process of its formation, for a correct 

 understanding of its structure. 



4. The Anus. — The anal tube is median, and opens on the middle 

 line of the tail in tadpoles of most Batrachians (fig. 2, B, an.). In 

 Rana and Hyla (fig. 2, A, an.), however, it is twisted to the right, 

 opening in the former genus close to the lower edge of the lower 

 caudal crest, higher up on the right side of the crest in the latter. 

 It is not long since that this difference in the position of the anus 

 was first observed. Goette (Entwick. d. Unke, p. 677, 1875) fancied 

 that the dextral anus constantly accompanies the sinistral spira- 

 culum, and his error has recently been repeated bv Spengel (Zool. 

 Anz. 1888, p. 339). But I showed in 1884 (Ann. & Mag. N. H. 

 xiv. p. 390), and again in 1886 (Bull. Soc. Zool. France, 1886, 

 p. 319), that such a correlation exists only in the genera Rana and 

 Hyla, the Toads and Pelobatoids having the median anus together 

 with the sinistral spiraculum. 



5. The Lines of Muciferous Crypts. — All tadpoles are provided 

 with these organs, the homologues of the lateral line in fishes. 

 Their existence, long overlooked, and their signification as organs 

 of a special sense, were first pointed out by F. E. Schulze (Arch, f, 

 Anat. u. Pliys. 1861, p. "/&?), whose researches into their structure 

 were supplemented by himself (Arch. f. mikr. Anat. vi. 1870, p. 62), 

 Leydig (N. Acta Ac. Leop.-Carol. xxxiv. 1868, p. 46), and Malbrane 

 (Zeitschr. f. wiss. Zool. xxvi. 1875, p. 24). For further notes on 

 the disposition of these lines we are indebted to Lessona (Atti Ace. 

 Lincei, 3, i. 1877) and Lataste (Actes Soc. Linn. Bord. xxxii. 1879, 

 p. 308). The latter author, however, overrated the systematic im- 

 portance which is to be attached to these organs. It is a fact that 

 they may differ greatly as regards their degree of development in 

 individuals of the same species, and their arrangement also varies, 

 within certain limits, irrespective of the species. I have found them 

 usually most distinct in Pelodytes, Rana agilis, R. latastii, and Bombi- 

 nator igneus, least in Bufo. The most distinct and constant appear 

 to be the lines situated on the head, passing between the nostrils and 

 bordering the eyes. I append figures (fig. 3, p. 598) of tadpoles of 

 Rana agilis, Pelodytes punctatus, and Alytes obstetricans, in which 

 these organs are represented by dotted lines. In addition to these 

 lines all tadpoles show more or less distinctly a small whitish gland in 

 the middle of the head between the eyes, the so-caWeA frontal gland 

 (Stieda, Arch. f. Anat. u. Phys. 1865, p. 52 ; Lessona, Atti Ace. 

 Tor. V. 1880, p. 581 ; H. de Graaf, Bijdr. tot de Kenn. v. d. Bouw 

 e. d. Ontwikk. d. Epiphyse b. Rept. e. Amph., Leyden, 1886), and a 

 glandular streak, extending ft-om the nostril towards the eye, the 

 lachrymal gland (Born, Morph. Jahrb. ii. 1876, p. 611, figs. 23 

 &24). 



6. Pigmentary Network. — In addition to the ordinary pigment- 



