DEVELOPMENT OF GONAD AND GONODUCTS IN CHITON-. <>7 



organ as in the solenogastres. At all event- thefe are no signs 

 -.1 di-tinct branches penetrating the gland as in the later sta^ 



About the time of the fusion of the gonad cavities t when the 

 length ol the body is approx'mately I mm.', in a stage slightly 

 earlier than the one represented in Fig. 3, each gonoduct ari-c- 

 as a -lender evagination of the postero-latcral walls of each halt 

 of the reproductive gland. These grow rapidly, and in contact 

 \\iih the pericardia! wall proceed laterally and vcntrallv until 

 they come iii contact with the ectoderm of the mantle groove. 

 In the formation (A the outer opening the ectoderm cell- appear 

 inereK to -eparate: if an ectodermic diverticulum i- formed it i- 

 evidently \ery short and transitory. 



In later -tages the proximal ends of the gonoduct- -hilt lor- 

 \\ard -li'Jitlv , and are attached to the dorsal side (l-'k. - <t the 

 '^onad close to tin- mid line. During this process ilu-ir \\all- 

 thii ken, and at the height of the breeding season there an -i^n- 

 ecretor) activ ity on the part of the component cell- especially 

 in the mi-hborho(Ml of the reproductive organ. Th of 



boih of these species are held in the mantle cavity, and are lo.i-dv 



1 it niiii 1 t' p'^ei her possibly by this secretion ol the o\ id in t . 



Ilie i. nl\ niluT observations bearing on the development ol 

 the ^oimdin i- are those of Plate 1 who has made the claim lh.it 

 in the \oiiiii; <f Acanthopleura echinata, 15 mm. in length, the 

 gonad i- completely separated from the gonoduct s that , a- -lender 

 divert ieiila. are connected with the mantle cavity and are a< 

 cordinglj 'iodermii-. drained that this is the true state o| 

 a Hair- in .1 . ft hinatu it is unprofitable for the prc-ent to attempt 

 to correlate the two t\ pes of development when only three -pe. n - 

 ..I .hitoii- have been examined on this point. Hov\ever, it i- 

 inti-re-tini; to note that in several species of California chiton-' 

 three millimeter- or less in length the gonad and it- duct- are 

 attached and open to the exterior. In some species, -nch as 

 h, hncuhiton iundalencnsis, the ducts are highly glandular and 

 it i- 1 1.. il.le, though it appears to us improbable, that this 

 -landulai -eciion is of ectodermic origin. 



i/ ' -iippl. .1 (Fauna Chilensis, Vol. i 



: Il.atli, Zoo/. Jahrh., Bd. 21. p. -29. 



