140 CRESSWELL SHEARER, WALTER DE MORGAN, H. M. FUCHS. • 



there is considerable evidence for the contention put forward by Loeb, 

 King, and Moore (10) that the minor skeletal characters are inherited 

 independently of either parent. We are able to bear out their state- 

 ment that with regard to the apical rods, the spinous condition of 

 which is dominant over the smooth, and the clubbed condition over 

 the arched, quite independently of their origin either from the paternal 

 or the maternal side. 



3. Eegarding the early larval characters, therefore, as of too variable 

 a nature, we have reared the normal and hybrid crosses to the young 

 Urchin stage, in the hope of finding, in the late development, more 

 definite characters for the solution of the question of inheritance. 

 In the presence or absence of the posterior ciliated epaulettes, of the 

 green pigment masses and of the posterior pedicellaria, we claim that 

 we have found such definite characters, and we find them to be invari- 

 ably inherited through the egg. A full summary of these facts has 

 already been given in § IV, page 135. 



4. We have shown that an alteration of the alkalinity of the water 

 affects the inheritance neither of the skeletal characters nor of those of 

 the late larva. 



5. The young hybrid Urchins, some of which have already reached a 

 considerable size and are now two years old, are, in superficial appear- 

 ance, of the pure motherly type. 



6. We suspect that a considerable amount of hybridization occurs 

 under natural conditions between E. csculentus and £J. acutus. 



LITERATURE. 



1. Allen, E. J., and Nelson, E. W. On the Artificial Culture of Marine Plankton 



Organisms. Joum. Marine Biol. Assoc. Vol. vil, p. 421. 1910. 



2. Bell, F. J. Catalogue of the British Echinoderms in the British Museum. 



London. 1892. 



3. Boveri, T. Ein geschlechtlich erzeugte Organismus ohne miitterliche Eigens- 



chaften. Ber. d. Gesf. Moqih. ». Phys. Miinchen. 1889. 



4. tjber die Befruchtungs und Entwickelungsfahigkeit kernloser Seei- 



geleier und iiber die ]Moglichkeit ihrer Bastardierung. Arch. fihr. 

 Ent. Mech. Vol. il, p. 394- 1895. 



5. Doncaster, L. Experiments on Hybridization, with special reference to the 



effects of conditions on Dominance. Phil. Traits. Roy. Soc, London. 

 Ser. B. Vol. cxcvi, p. 119. 1903. 



6. Driesch, H. IJber rein miitterliche Charaktere an Bastardlarven von Echiniden. 



Arch.fiir Ent. Mech. Vol. vii, p. 65. 1898. 



7. Uber Seeigelbastarde. Arch. filr. Ent. Mech. Vol. xvr, p. 713. 1903. 



8. Fischel, A. Uber Bastardierungsversuche bei Echinodermen. Arch, fiir 



Ent. Mech. Vol. xxii, p. 498. 1906. 



9. Hagedoorn, A. L. On the purely motherly character of the hybrids pro- 



duced from the eggs of Stronyylocentrotus. Arch, fiir Ent. Mech. 

 Vol. XXVII, p. 1. 1909. 



