81 \r-ii.i n "i i HI I.I.M t: \. 



cic:it rice i-> the \rli-_[c of : HI opeiiini: which placed thi^ n\ i^,-i< k 



in communication with the initial air-chamber of the shell ; imi 



lie h:is nr\rr seell this BllppOSCCl \i>;ick. which i-> hypothetical. 

 For him. I he Nautilus is ;i cej)halopod \\hich ha> lo-.i il-> ovi- 



ack. 



Ill Aimnmiitr* :ind < Innial i! es t he initial disp<it inn is riilin-ly 

 diH'crciit . The u\ i^nck ispl:iinl\ visible, globular or ellipsoidal. 

 more lil:itcil NIMH the |>:irt <-nui i^nmis in the chambered ^pin-. 

 \i> ,-i ppr.M rniK-c <>t' :i cicn i rice, h >niliee>. consequently, in 



eviniine the tirs! ch:inil>ei- <>f M cephnlnpod t<> cl:iss it :Miimii- llie 

 N.-uililides or t!ie A niinnnides :IIK| ( Joni:il ides. 



M. H:iiT:m<li> li:is shown tli.-il the inili.-d :i|ipe:i r.-ince ot'tlie shell 

 of Niiiililns i> e\hiliite<l wi.honi ;in\ chini^e tlirnu^h .-dl the 

 ^eo|oLiic:d period> to tin- pi'eseni lime. The lis>mv is siippnv,.i| 

 l>\ M. I5:irr:inde to h:ive |)l;ice(i !he niolltisk cnnliiined in 1 he 

 initial chandler in cnimmmicaMon with a transitory oi'uan. eil her 

 a vitelline \cside ( which, to M . Fischer. ai)j)cars inadinissilile) 

 or to a natatory bladdiT. etc. 



From the first appearance to the final extinction of the (Jonia- 

 tid;e and A nnnonitidje. they always show a typical ovisack ; it i> 

 therefore inipnssiMc to derive sheni from the \aiitilida-. as snp- 

 po>ed by the developmentalists. This difference ha> induced M. 

 Mnnier-Chalmas (C'nnjtf*'* AV'//^///s. Di-c. -J'.ltli. is;:!) to separate 

 the two former from tin- tet raliranchiate or tent acn life rons cephal- 

 opoda ( Nantilida-). and to unite t hem with t he dil>raiichiatc or 

 acetalniliferoiis ^roup ( Spirulid;e and IJelemnit id;e ). which are 

 pro\ide<l with an ovisack. 



It still remains to ascertain whether the presence or absence 



of the o\i>ack has the systematic importance attributed toil; 

 what i> its nature and what is the purpose of the cicatrice. The 

 word ovisack may l>e badly chosen because it supposes the 

 c\i-1ence of calcareous envelopes to the e- 



One miirhl dis,-n-> and wonder a IOIILL time on t his subject 

 until a direct nlcrvalion on tin- emltryn^eny of Nautilus shall 



i/ive U-- the true solution. It i- tlm> t hat the question of the 



parasitism of the I'oiilpe of tin- Argonaut wax a._;i;:i!ed with 

 ardor until the day that Duvernoy showed the embryo of 

 to be provided with a shell in tin 



