TRIPLE MONSTROSITY— IN OTHER VERTEBRATES 37 



TRIPLICITY IN OTHER VERTEBRATES. 



Amphibia. Although re-duplication of parts is fairly common in the Amphibia (Gemmill ] ) 

 examples of triple monstrosity appear to he exceedingly rare. The nearest approach to the condition 

 that the author can find occurs in the Pdobutcs larva described by Bruch, 2 in which the axial parts 

 of the tail divide posteriorly into three. This condition, however, as in Barfurth's (8) Pelromyzon 

 larva, was probably the result of injury. 



Reptilia. A very early stage in the ring snake is figured by Wetzel, 3 in which there are three 

 centres of segmentation on the yolk, and one of the centres is itself double. In the older records, a 

 three-headed snake is stated to have been seen at Lake Ontario (Mitchill, quoted from Bruch, as 

 above, p. 172). Then there is also the account reported in Aldrovandi (# 427) of a snake with 

 three heads that was killed in the Pyrenees. 



The occasional formation, by way of supra-regeneration after injury, of a triple tail rudiment 

 (in Lizards), may also be mentioned here, as under Amphibia. 



Birds. Examples of triplicity in developing eggs have been recorded by : 



Dareste (58 p. 456, PI. XIV. fig. 5). Two blastoderms on the same yolk, one with a single 

 embryo, the other with two separate embryos, of which one is smaller than its neighbour 

 and has no heart. 



Dareste (as above, but Fig. 4). Three separate embryos on a single blastoderm. 



Dareste (as above, but only mentioned in note on p. 45 G). One area pellucida, with three 

 embryos united by the heads. 



Dareste (as above). Two blastoderms united together, one of them with a single embryo, and 

 the other with an embryo having two heads. 



Eauber. A common vascular area surrounding two areae pellucidae, one of which is small 

 and bears a single embryo, while the other has two embryos lying close together and 

 uniting by their adjacent body-walls. (Morph. Jahrb. Leipzig 5 167-190 Pis. XII. XIII.) 



Moriggia. A single blastoderm carrying three separate embryos. (Quoted from 247 3 p. 464.) 



Koch. An area pellucida carrying two embryos, one of which shows anterior duplicity. 

 (Quoted from 247 3 p. 465.) 



A case recorded by Tur should also be referred to here. I have only access, however, to the 

 very brief description of it given by Windle. 4 " There were four separate centres of development. 

 On three of these there was a primitive groove, and one of these grooves was double." 



Mitrophanow also figures a chick blastoderm with several (at least three) primitive streaks. 

 M.'s figure is reproduced by Schwalbe (222 ii. p. 26). 



Mammals. A few examples of unioval triplicity, but none of triple monstrosity, seem to have 

 been recorded since the publication of Taruffi's work on Teratology (247). This author very 

 properly emphasises the occurrence of unioval or homologous triplets in the human subject and in 

 other mammals, and refers such cases to an origin similar to that of identical twins, namely, the 

 development of more than one embryo from a single ovum (24-7 3 p. 450-460). More recent 

 instances of this kind are given by (a) Walla, (b) Breitschneider, and (c) Watson. 5 



Of triple monstrosity, Taruffi has collated eight examples in the human subject, four in the dog, 

 and four in the sheep (247 3 p. 465 et scq.). The accounts of these records need not be reproduced 

 here, and, indeed, the older records are often defective in respect of detail. Some of the cases will 

 be referred to in the notes appended to the following scheme suggested for the classification of 

 examples of Germinal Triplicity. 



'Supernumerary limb in a Frog, J. Anat. Physiol. London, 40 (387-395). 

 2 Ueber Dreifaehbildungen, Jenaische Zeitschr. Natw. 7 (142-175). 

 3 Drei abnorm. gebildete Eier von TropiJonolus natrix, Anat. Anz. Jena, 18 (425-440). 

 4 Report on Teratological Literature, /. Anat. Physiol. London, 40 p. 296. 



°(a) and (6). Quoted from Windle's Reports in J. Anat. Physiol. London, 37 p. 302, and 38 p. 365. (c) British Medical 

 Journal, Jan. 9, 1904 p. 75. 



