848 



SCIENCE. 



[N. S. Vol. III. No. 75. 



is not to be taken as diminishing the high 

 opinion of the merits of Prof. Lang's work 

 ■which we have already expressed. 



The bloodvascular system of moUusks (p. 1) 

 is not ' open ' in the ordinary sense of that 

 .word, but closed, though partly lacuiiary. 



In the true Diotocardia an intromittent male 

 ■organ is absent chiefly in the littoral species, 

 having been shown to exist in many deep water 

 forms such as Cocculina, Addisonia, Fissurella, 

 Solariella, many Puncturellidee, etc., and it 

 :should not, therefore (p. 4), be predicated of the 

 •entire group. The arrangement of the Txnio- 

 glossa is imperfect (p. 6); the Cajmlidce have a 

 retractile proboscis and are therefore not ' Eos- 

 trifera. ' The Columbellidx are not Txnioglosaa. 

 ■Janthina can hardly be called siphoniferous. 



The nudibranchiata are not all destitute of a 

 mantlefold (p. 10), at least if that fold be de- 

 fined with any consistency, e. g., Pleurophyllidia. 



The gymnosomatous pteropods (p. 11) do 

 not feed chiefly on T hecosomata, but on hydro- 

 zoa. The absence of a mantle is merely nomi- 

 nal, that organ being coincident with the integ- 

 ument, in any practical view. The arrangement 

 -of the Decacerate cephalopods is antiquated 

 (p. 24); Spirilla is undoixbtedly Oigopsid. 



Throughout the work (cf. p. 26) couchioline 

 is more or less confused with chitine. The 

 periostracum of bivalves is referred to as chiti- 

 mous, by the majority of writers, as well as 

 Lang, but long ago Loew showed that the chitine 

 of mollusks (jaws and radula) does not give a 

 saccharine reaction with sulphuric acid, and is 

 not therefore identical with ordinary chitine, 

 while the conchioline of the periostracum and 

 test is purely horny, dissolving with ease in 

 liquor potassse and in no respect chitinous. 



The spines of Amphineura are homologized 

 with the shell of Chiton (p. 29) and later the 

 tegmentum of the chiton and its ' aesthetes ' are 

 correctly homologized with the corium of the 

 girdle and its spines ; it seems surprising, there- 

 fore, especially when the embryologjf of 

 Dondersia and Chiton is considered, to find (p. 

 40) an attempt at homologizing these cuticular 

 structures not only with the true shell (articu- 

 lamentum) of Chiton, but even with the shell of 

 mollusks in general. The shell of Argonauta 

 (p. 38) is a product of secretion from the cuticle, 



serving the purpose of an oophore, and should 

 not be homologized with the protoconch and 

 concha of other cephalopods. The figure of 

 Chitonellus (more properly Cryptoplax) is taken 

 from a very contracted spirit specimen and 

 fails to show the proper proportions of the foot. 

 Speaking of the concrescence of the mantle 

 margin in Pelecypoda (p. 51), it should be 

 stated that several superanal foramina occur in 

 Naiades occasionally, and the fourth ventral 

 orifice in Pholadomya, etc., is with little doubt 

 correlated with the opisthopodium and not with 

 the byssus. We find no reference to the opistho- 

 podium in the book. The extensive concres- 

 cence of the mantle edges (p. 52) is not ' always ' 

 accompanied by ' well developed siphons, ^ e. g., 

 Tridacna, Chania; and the same examples show 

 that the statement that in sessile forms the 

 mantle is found completely open is far fi-om 

 being generally true. 



In discriminating the ligament and resilium 

 the latter is said (p. 61) to be elastic and the 

 former not so ; in fact, both are elastic and the 

 resilium adds resiliency to its tensional elas- 

 ticity. Paleontology shows the error of the 

 statement (p. 63) that the Pectinidee are pro- 

 bably derived from sessile forms. The gape in 

 many bivalves is accounted for (p. 64) by ' the 

 greater development of siphons and foot ' which 

 is merely an incident of the gaping; the true 

 reason is to be sought in the less need of shelly 

 protection among deep burrowers; Pholads (p. 

 65) are said to rasp the stone by the edges of 

 the valves. While this is true of certain forms 

 like Teredo, in many others, including most 

 Pholads, the rasping is done by the surface of 

 the foot. The snout in Captthis (p. 102) is er- 

 roneously stated to be not invaginable. It is 

 really invaginable from the base, much as in 

 Bolium. The filamentous ' tentacles ' (=: cap- 

 tacula) of Scaphopods are not homologous with 

 the tentacles of Gastropoda. In treating of the 

 epipodium, mention might have been made of 

 its modification to serve as a seminal conduit in 

 certain Trochids. The Unionidee (p. 115) are 

 not, as a rule, mud dwellers. The musculation 

 of Chiton (p. 120) has recently been fully de- 

 scribed by Lillian Sampson. The statement 

 that the muscles of mollusks are never striated 

 (p. 119) is not true literally (p. 124), but the 



