016 T. IKEDA : 



tlio convex dorsal side. The nuclei in all tlio Idnstodermal cells 

 are always situated in a ]>eri plierai position. 



Plasmic corpii^cle><. — A notewortliy fact with regard to the 

 l)lastula is that in its older stage a certain nunil^er of small and 

 non-nucleated ])lasniic spheres is almost constantly met with in the 

 blastocœlic cavity (fig. 2ö, pl.co.) These have l)een first described 

 hy FoETTiNGER uuder the name "corpuscules mésodermiques." 

 According to this author, these corpuscles are free nuclei imbedded 

 in a connnon ])r()t(»]dasmic mass which is supposed to fill up th(> 

 Itlastocd'le, each coi'jnisclc bocoming a mesoblast cell, after appro- 

 priating to itself a certain portion of the surrounding protoplasm. 

 This view of Foettinger, which certainly can not be accepted 

 at the present day, was, I believe, partially due to the then 

 defective technique. His method consisted in pouring dilute acetic 

 acid over the living eml)ry(», and this, as the author himself was 

 well aware, is highly detrimental, in that it frequently In'caks up 

 llie blastomeres into fragments. The corpuscles described by him 

 fi'(jm so early a stage as that with only 8 ))lastomeres must have 

 l)een simply produced l)y fragmentation, the result of his drastic 

 treatment. The connnon protoplasmic mass supposed to be present 

 in the blastocœle, was probably nothing l)ut a coagulum. 



Again the mesodennzellen which Metscknikoff ('82) found 

 m the blastocœlic cavity of the blastula are certainly not true 

 mesoblast cells l)ut rather certain spheres similar to Foettin- 

 (ier's " corpuscules mésodermiques," as was rightly pointed out l)y 

 Caldwell. Eecently E. Schultze ('97) pul)lished a short paper 

 entitled " Ueher die 3[esodcrinhiIdung bel Phoronis,'" in which he 

 writes as follows: — ''Schon, auf dem Stadium- der rundliehen 

 Blastida sehen leir einige Jlesodermze/len im Blastoeed riuf sitzten " 



