872 THE AMERICAN NA TURALIST. [Vol. XXXV III. 



plasm and a great many yolk granules enclosed by a sharp cell 

 wall. In the centre of the cytoplasm there is a nucleus or more 

 than one. These structures are not the ordinary yolk cells 

 lesultmg fiom segmentation ot the cndodermal i)art of the origi- 

 nal ovum, but according to MacMurrich ('87) they are unferti- 

 lized ova which were discharged into the egg capsule by the 

 mother at the time of its formation togethei with the tiue'e^gs. 

 lie sa)s "each egg ca])sule contains a large number, perhaps 

 tuo bundled ot .na nKasutim, about 025 m^m acioss . of these 



>i si\ dexclop, the rest being su allowed b\ the 



.s and used as tood The non-de\ eloi)mi; o\a 

 " s^,-,nKiU noi push out polar globules, nor do they 

 1 "1 dismtL^uite, but are ingested by the embryos so 

 ^ail) one ot tbese api:»ears to consist of a large 



•'^a bound together into a ball." The embryo of 

 1.^ thus \cT\ unlike that of related j^rosobranchs such 

 n uhuh the xoik IS a put ot the oiiomal stiuctuie of 

 -I'^^l Ikuii i).ut ol ilic eiidoderm of the embryo, 

 i-^"lnn ihL s<.^nKnts and uac lies the gastrula 



tlun suaPou. thL othei e-us ,t^elf ha\ ing no supply 

 llH- ma thus swallou-ed I shall call food ova. 



al kidiKxs aiL conspicuous organs in man\ proso- 



