556 The A nintal Kingdom 



These animals are monoecious, but cross-fertilization is ensured. 

 The ovaries are located in the posterior lateral portion of the trunk 

 coelom, while the testes are in the lateral anterior region of the tail 

 coelom. From the testes, paired vas deferens pass posteriorly to the 

 seminal vesicles. The sperm are released into the sea water as bundles 

 of spermatophores, which are picked up by other worms, and the sperm 

 are stored in seminal receptacles. The seminal receptacle is a bulblike 

 projection of the oviduct. A fertilisation tube grows from this re- 

 ceptacle to the ripe ovum lying in the ovary. The sperm pass up the 

 tube and fertilize the egg. The zygote then passes through the wall 

 of the oviduct into the cavity of the oviduct and out. The eggs hatch in 

 about two days into a larval form closely resembling the adult. 



While the number of individuals of this phylum may at times be 

 extremely high, there are but few known species. Undoubtedly they 

 are important as food organisms for larger animals. Sagitta is the 

 commonest genus. 



The Phylum Enteropneusta (or Hemichordata). — The position 

 of this phylum in the animal kingdom is subject to different interpreta- 

 tions. The members possess pharyngeal gill slits and some have a dorsal 

 tubular nervous system, both of which are considered characteristics of 

 the phylum Chordata. For this reason many zoologists prefer to con- 

 sider them as a subphylum of the phylum Chordata. On the other hand, 

 they lack a well-developed notochord. A small strengthening rod in the 

 anterior end has at times been considered as homologous with the noto- 

 chord. Since this is subject to some question, it may be best to consider 

 them as a separate invertebrate phylum closely related to the inverte- 

 brate-chordates. 



The members of this phylum are commonly called the "tongue 

 worms" or "acorn worms" due to their possession of an anterior pro- 

 boscis. They are widely distributed throughout the shallower parts of 

 the ocean and a few are found in deeper waters. In all, about 60 species 

 are known, but due to their habit of burrowing in the soft bottom ooze, 

 it is probable that there are many more to be discovered. In size they 

 vary from 2 inches to 2 feet. One common genus is Saccoglossus, 

 species of which are found in many parts of the world. 6*. kowalevskii 

 is the species most commonly found along our east coast. It lives just 

 below the low tide zone from Massachusetts to North Carolina. 



Externally the body consists of three well-defined regions : the an- 

 terior proboscis, the short collar, and the long trunk region just behind 

 the collar. 



