GEJ^ERxiTIVE ORGANS OF MOLLUSCA. 387 



tubes, wlaich ai'e placed in the anterior region of the animal ; their 

 short eiSerent ducts open beside the generative orifice. Their 

 secretion appears to cement the ova together; and these, in most 

 Cephalopoda, are united into racemose groups. In front of the 

 nidamental glands there is a pair of smaller glandular organs, which 

 consist of closely-coiled tubes, and have the same function as the 

 other set of glands. 



A similar capsule (Fig. 205, c) to that found around the ovary 

 encloses the testis {t') ; this organ is made up of a number of 

 branched c^cal tubes united together. These tubes are likewise 

 attached to the wall of the capsule, so that in this case also the 

 germinal matters first pass into the capsule, and then into the vas 

 deferens, which is continuous with it. This duct is a much-coiled 

 and gradually- widening canal (ve), so that it forms a seminal 

 vesicle. Glands are embedded in the walls of its widened portion, 

 and in many cases part of the wall is converted into a larger 

 glandular organ, so that this part has yet another function. One or 

 two other distinct glandular appendages (g) are found in various 

 Octopoda. All these glandular differentiations of the wall of the 

 vas deferens secrete matter which is mixed with the sperm, and 

 which is used to form the special seminal ropes. At the end of the 

 glandular portion, or after uniting with these ducts, the seminal 

 duct is considerably enlarged, or pushed out on one side (Sepia, 

 Loligo) ; this modification may also be converted into a considerable 

 appendage {hN) (Octopus), These "pouches of Needham" serve as 

 receptacles for the seminal ropes or spermatophors, which are 

 formed in the glandular portion of the seminal duct. The rest of 

 the duct is continued, with but little change, into a papilliform pro- 

 cess, which is placed on the left side in the mantle-cavity (Fig. 1 78, 

 g), or it opens to the exterior at the base of such a papilla. We 

 have already described the way in which single arms become func- 

 tionally connected with the generative apparatus in many Cephalopoda 

 (§254). 



The formation of spermatophors, which is a comparatively 

 rare thing in the Gastropoda and in the other divisions, is the rule 

 in all the Cephalopoda, and is in them most complete. As a rule, 

 one of these seminal ropes forms a long cylindrical structure, on 

 which several envelopes may be distinguished. The contents of the 

 tube are only partly seminal, for in each spermatophor there is a 

 special substance which occupies the hinder portion, and which we 

 may call the exploding mass. The sperm is invested in a tubular 

 manner by a special coat, and is placed in the anterior division of 

 the spermatophor. Behind it is the anterior flattened end of a long 

 and spirally-coiled band, which extends through a large portion of 

 the spermatophor, and is continuous at its hinder end with the outer 

 coats. The substance of this spiral band is the exploding mass. 

 When it comes in contact with the water, the spiral band immediately 

 begins to elongate, and drives before it, and to the front end of the 

 spermatophor, that part which encloses the semen. 



2 c 2 



