On 8p07itaneous Division in the Echinodermata. 323 



' EXPLANATION OF PLATE XII. 



Fig. 1. Homopus siguatus. 

 Fig. 2. Kinixys erosa. 

 Fig. 3. Geoemyda spiuosa. 

 Fig. 4. Geoemyda grandis. 

 Fig. 5. Eninienia Grayi. 

 Fig. 6. Emya Fraseri. 

 Fig. 7. Chrysemys picta. 

 Fig. 8. Trachemys Holbrookii. 

 Fig. 9. Pseudemys concinna. 

 Fig. 10. Bellia crassicollis. 

 Fig. 11. Damonia macrocephala. 

 Fig. 12. Damonia Reevesii. 

 Fig. 13. Platysternon peguense. 

 Fig. 14. Cuora amboiueusis. 



XLIII. — On Spontaneous Division in the Echinodermata and 

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



It is only in a few specimens of Ojphiothela 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 difference 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 with 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 slightly abridged by W. S. Dallas, F.L.S., from a 

 paper entitled " Ophiuridarum novarum vel minus cognitarum descrip- 

 tions nonnullse," published in the Oversigtover det K. Dansk. Vid. Selsk. 

 Forhandl. 1872, pp. 108-158, French summary, pp. 30-54. 



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

 clusion of this paper. 



