THK DEVELOPMENT OF THK GONAD AM) GONO- 

 I)t;CTS IN TWO SPECII-> ' >F CHITONS. 



ROSE M. HK;LEV AND HAROI D HEATH. 



Tin- I. HIT development of the chitons ha- never been fully 

 iim-Mi'-.m-cl. and the fragmentary obscr\ MI i m- that have been 

 in. idi- relate .ilmost exclusively to immature form> in very ad- 

 Nam id stages. Accordingly we are at piv-ein alimt whollv 

 ignorant i.i tin- development of the principal systems of organ^ 

 .nid ilu-ir homologies. Many of the more import, uu i|iie-timi- 

 relating to 'In se animals center in the formatinn of tin i-u-lmn, 

 .md ii \\.i- \\iih the hope of throwing some light <>n thi> >ul>iect 

 tli.it tin- piv-eiit work was undertaken. 



111. iu< -prcies that form the basis of thi> investigation, 

 .hyiit-nnon ra ynwndi and Xutlallina tlwmasi, .\n- !.iirl\ almn- 

 il.mt li.ini- in certain localities along theci>.i-t <>i ( '.ilifnrni.i, and 

 n\\iiiv; tn tln-ir Miiall si/e are readily snt \< uinl. The tK i---\\ ini- 

 iniii^ young 1 were placed in aquaria together \\itli t'lMgnu-nt- uf 

 -ln-ll- . 'i!ns californica on which they Imallv -i tiled alter 



partialK completing their metamorphosis. Tlu-v \\(ic then 

 traii-lenvd to small and protected tide pm.U \\hen- tln\ de\el- 

 "|ird mu inalU' and in se\ - eral instances were allowed t" re.n h the 

 -exualK mature condition. Precautions \\eiv taken to keep the 

 \ i ni nv; i >l eaeh -pe. ies in separate pools and it \\ a- I mi ml that they 

 travel essen dally the same developmental path tm- a Ion- period. 

 I >i-tiiiL;tii-liiiig characteristics accordingly appear late, in I'aet 



roii-idt -ralil\ lievond the formation of the L;<'iia<l ami it- dm I-. 

 It U to In- understood therefore that while the tigure> are of 

 T. niynnuii the\ -erve equally \\ell tor A", tlnnintsi. 



\\ a \ei\ earl\ stage the heart and peril ardial cavity are 

 dexeli.pe.l troni (clU, giving evidence of lu-ing derixed exclu- 

 >i\el\- from the -e. .-mlary mesolila-t pm-eiu ot 4/>i, whieh 

 lorm-> an irregular la\er mi the poMcro-dm--al -ide ot the larxa. 

 A rel.n : \el\- long period of tinu- then ensues, during which the 



iii.u li.iliit- <>i tli> e /'./. In Bd. XXIX.. \i. ij. 



95 



