2-14 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The musculature is divided into a dermomuscular tube and muscles of 

 the body-cavity ; the former consists of a wide-meshed plexus of band-like 

 longitudinal and circular muscles, which exhibit a division into primitive 

 fibrils and posterior pieces ; the longitudinal muscles are branched. The 

 muscles of the body-cavity have their origin in the skin, and are either 

 inserted into the segments of the body or into internal parts ; they consist 

 of contractile fibre-cells with homogeneous cortex and plasmatic axis, and 

 they act more energetically than the dermal muscles. The cilia of the 

 wheel-organ are separated on each hemisphere by a circular groove ; in the 

 lower circlet there are cilia which are directed towards the mouth. The 

 buccal cavity is infundibuliform, and passes into a laterally compressed 

 CBSophagus. The wheel-organ is withdrawn by three homogeneous muscular 

 fibres. From a study of this organ it is clear that, for a cilium to produce 

 its eftect the return must be slower than the blow or beating movement ; 

 the buccal cavity is able to divide into two cavities, the dorsal of which 

 effects the indrawing, and the ventral, the removal of the corpuscles sus- 

 pended in the water. 



The terminal portion of the proboscis is beset with active cilia which 

 are protected by two hyaline membranes ; it contains a ganglion which is 

 connect(;d with the cerebrum by two strong nerves, and supports sensory 

 cells surrounded by supporting cells. These last are jn-ocesses of the 

 hypodermis, which is itself connected with the hypodermis of the wheel- 

 organ by a broad plasmatic band ; the hypodermis is thickened above the 

 ganglion. 



The foot does not contain any of the organs specially belonging to the 

 trunk, such as the enteric or excretory organs, but is in direct connection 

 with the coelom. The glands in it consist of four rows of uninuclear gland- 

 cells, and an unjiaired piece to which the rows are attached. The pharynx 

 consists of two jaws with the jiroper musculature, and an elastic membrane 

 which bounds the api:)aratus anteriorly ; the dental formula is f. Two 

 dorsal uninuclear and three ventral multinuclear salivary glands surround 

 the pharynx ; the oesophagus has a dorsal gland, and the stomach or chyle- 

 intestine three pancreatic glands, which consist of a thick syncytial tube 

 with numerous cell-nuclei, and a richly ciliated cuticle towards the lumen. 

 It is attached to the dorsal integiunent by connective-tissue fibres, and is 

 closed at its end by a muscular sphincter ; the rectum has great powers of 

 enlargement. 



The central portion of the nervous system is an elongated pyriform 

 cerebrum, the dotted substance of which lies in the centre sui-rouuded by 

 closely appressed nerve-cells ; the peripheral nerves are sharply distin- 

 guished into groups for the anterior end and for the trunk. At the base 

 of the tentacles and at the origin of the tentacular nerves there are several 

 rounded cells ; two nerve-fibres are stretched between the bases of the 

 tentacle and the ganglion of the j^roboscis. There are two pairs of trunk- 

 nerves, and these are finely gi-anular. 



The excretory organ consists of the contractile bladder, the ducts, and 

 the ciliated lobes ; in front of the opening into the bladder the tubes are 

 constricted, and this arrangement prevents the return of fluid on the 

 contraction of the bladder. 



Males were never observed ; the female generative organs are yolk- 

 glands provided with highly granular and very bright large nuclei, which 

 appear to be separated from the smaller germarium by a membrane ; the 

 ovum, consequently, appears to be nourished by a process of diosmosis. 

 The whole organ is surrounded by a nucleated membrane ; in the ripe con- 

 dition the vitcllarium and germarium form a syncytium, but in the un- 



