GENERAL ZOOLOGY 



Nerve ring Pharynx 



Mouth Excretory 

 pore 



Intestine Oviducts Ovaries Pseudocoel 



Anus 



Pseudocoel 

 Muscles 



Cuticle- 

 Epidermis ' 



■ Ovary and 

 oviduct 

 Nerve cord 



Muscle 



Epidermis 

 Cuticle 



Fig. 12.4. .hearts lumbncoides: e;eneral features of internal anatomy- A, dissection of a 

 female, lateral view; diagrammatic. R, cross section in the midregion of the body- C, 

 lons;itudinal section, posterior end of the male. D, female reproductive system. E, male 

 reproductive svstem. (Modified after R. Leuckart, 1876, Die menschlichen Parasiten.) 



cuticle, which must be molted periodically to permit growth of the individual. 

 In free-living forms the cuticle often bears special structures, such as hooks, 

 spines, and bristles; these usually function as locomotor appendages, as tactile 

 organs, or as mouth parts to aid in feeding. Nematodes that are parasitic as 

 adults are usually without such special structures, except for horny teeth and 

 plates in the buccal cavity. In general, as among the Platyhelminthes, the 

 parasitic forms appear to have undergone structural simplification in adapta- 

 tion to their mode of life. 



The simple epidermis of the body wall is underlain by a layer of peculiar 

 muscle cells, usually organized in longitudinal bands. The typical muscle 

 cell consists of a central cytoplasmic mass which contains a nucleus and gives 

 rise to tremendously elongated contractile processes lying lengthwise under- 

 neath the epidermis. The muscular layer forms the external boundary of the 

 pseudocoel, which contains a fluid presumably functioning in the transport of 

 nutrients and wastes. The digestive tract is usually complete, consisting of a 

 mouth, a muscular pharynx, an elongated intestine, a rectum, and a posterior 

 anus. The intestinal epithelium, a single layer of tall, columnar cells bounded 

 internally by a cuticular border, functions in whatever digestion may be 



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