MOLLUSCA. 823 



impossible that the spermatophore may be transferred in some cases, 

 in the way supposed by VOGT, but not always. For the spermatophore 

 has been found in the hectocotylus, whilst the filament was yet in- 

 closed in its proper sac. In this case the other arms may have 

 effected the transfer, as LEUCKART conjectures. After it has been 

 brought thus far, the propulsive force of the spiral portion of the 

 spermatophore must be supposed to come into play in order to begin 

 the passage through the tube of communication with the muscular 

 pouch of the hectocotylus, whose walls are also muscular. The fila- 

 ment at the end of the hectocotylus has been very generally supposed 

 to act as a penis. H. MUELLER found as many as six of them 

 within the capsule of the ovary in Argonauta Clio, that had been 

 broken off', and two others in one of the oviducts, so that no fewer 

 than eight males would seem to have fecundated this individual. 



It is presumed that when the hectocotylus arm has been cast off, 

 it may be successively reproduced.] 



The eggs are laid in heaps, or are connected with each other in 

 clusters by pedicles and an adhesive substance. In this respect 

 great variety prevails in the different genera. In Loligo, many eggs 

 are united in strings of a gelatinous substance; in Sepia they are 

 very large and surrounded by a horny dark envelop, which is pro- 

 duced into a pedicle at one extremity, and by which the eggs are 

 attached to each other, or to foreign bodies. 



In the development of the embryo, when the egg has been laid, 

 grooves are formed in that part of the yolk where was previously 

 the germinal vesicle, and which do not extend over the whole 

 yolk. Here the embryo afterwards appears as a disciform germ, at 

 first flat and round, in which, at an early period, different inequali- 

 ties indicate the first existence of the mantle, of the eyes, and of the 

 funnel, formed at first of two separate halves. This germ-disc be- 

 gins to swell gradually in the center, extends itself constantly further 

 towards the circumference, and finally surrounds the entire yolk. 

 In this way a part of the yolk-sac between the arms at the ventral 

 surface is included in the mantle, so that afterwards an internal as 

 well as an external yolk-sac is found, the two being connected by a 

 narrow pedicle 2 . 



1 [Op. cit. p. 354.] 



8 Formerly it was supposed that the yolk-sac is connected with the mouth by means 

 of this pedicle (CAVOLINI) ; CUVIER presumed a connexion with the oesophagus ; see 

 his memoir sur Us ceufs de Seiches. Nouv. Ann. du MM. I. 1832, pp. 153 160, PL 8. 

 The chief work that we now possess on the development of these animals and from 

 which we have borrowed what has been announced, is A. KOELLIKER Entwickelungt- 

 geschichte der Cephalopoden, Zurich, 1843, 4*- 



