The Occurrence of Situs inversus among 

 artificially-reared Echinoid Larvae. 



By 



Hiroshi Ohshima, 



Assistant Professor in the Department of Agriculture, Kyushiu 

 Imperial University, Fukuoka, Japan. 



With 3 Text-figures. 



Contents. 



PAGE 



1. Introduction .......•• 105 



2. Descriptions of the Larvae with Inverse Situs . . 107 



3. Results of the Experiments 113 



4. Changes which may possibly have taken place during 



Earlier Stages 117 



5. Variations among Double-Hydrocoele Larvae and other 



Abnormalities . . . • • • • .110 



6. Considerations on the Organs and Structures concerned 



AND THE Factors concerned in their Development . 128 



7. Probable Mechanism whereby Abnormalities are pro 



duced ...•••• 



8. External Factors as Causes of Abnormalities 



9. Summary and Conclusion .... 



10. Literature Cited 



11. Appendix 



139 

 143 

 145 

 146 

 148 



1. Introduction. 



A REMARKABLE case, wliere a hydrocoele and its associated 

 structure had developed only on the right side instead of on 

 the left side of the Iwdy, as in normal specimens, came under 

 my notice among tlie artificially reared larvae of Echinus 

 m i 1 i a r i s . 



