On Sjyontaneous Division in the Ecfdnodermata. 323 



EXPLANATION OF PLATE XIL 



Fig. 1. riomopus signatus. 

 Fig. 2. Kinixys erosa. 

 Fig. 3. Geoemyda spiiiosa. 

 Fig. 4. Geoemyda graudis. 

 Fig. 5, Emmenia Grayi. 

 Fig. G. Emys Fraseri. 

 Fig. 7. Chrysemys picta. 

 Fig. 8. Trachemys Holbrookii. 

 Fig. 9. Pseudemys coucinna. 

 Fig. 10. Bellia crassicoUis. 

 Fig. 11. Damonia macrocephala. 

 Fig. 12. Damonia Reevesii. 

 Fig. 13, Platysternon peguense. 

 Fig. 14. Cuora amboineusis. 



XLIII. — On Spontaneous Division in the Echinodermata and 

 other Radiata. By Dr. C. F. Lutken*. 



It is only in a few specimens of Ojjhiothela isidicola^ sp. n.f 

 (from Formosa), that I have found the six arms equal or nearly 

 so : in most individuals of moderate size the three arms of one 

 side are larger than those of the opposite side ; and in this re- 

 spect we find all possible intermediate stages, from specimens 

 with three arms well developed and three scarcely perceptible, 

 to others in which the diiference is insignificant. Moreover 

 we find nearly as many specimens having only three arms and 

 the corresponding half of the disk (as if they had been cut 

 with a knife into two equal parts) as of completely developed 

 individuals with six equal arms. There is no doubt that a 

 division has taken place, at least in the case of those which 

 have only three arms, or three large and three small ones, and 

 that the halves produced by this division have the power of 

 replacing the missing half both of the disk and arms. It is 

 only witii regard to the minority which are furnished with six 

 equal arms, and in which the two halves of the disk are equally 

 developed, that there can be any doubt ; for although the greater 

 part of the individuals of this species may be destined to un- 

 dergo division, we must not conclude from this that all are so. 

 Whether the division is repeated several times in this Ophi- 

 urid I cannot decide with certainty ; but the series of specimens 



* Translated and sliglitly abridged by W. S. Dallas, F.L.S., from a 

 paper entitled " Ophiiu-idarum novarum vel minus cognitarum descrip- 

 tiones nonnuUoe," published in the Ovcrsigtover det K. Dansk. Vid. Selsk. 

 Forhandl. 1872, pp. 108-158, French summary, pp. 30-o4. 



t The Latin characters of the new species will be given at (he con- 

 clusion of this paper. 



