THE EXCRETORY AND CIRCULATORY SYSTEMS 

 OF CRYPTOCHITON STELLERI MIDD. 



HAROLD HEATH. 



Somewhat over half a century ago Middendorff ('49) published 

 his extensive studies on the anatomy of Cryptochiton stellcri, the 

 largest and in some respects the most highly modified of the 

 chitons. In several important details this was a decided contri- 

 bution to our knowledge of the group and yet the work has not 

 received the attention it has merited chiefly for the reason that 

 the facts are inextricably associated with numerous errors (due 

 to poorly preserved material) and are illustrated by figures often 

 difficult to interpret. It is the purpose of the present paper to 

 explain and to a certain extent correct Middendorff's results and 

 especially to describe some of the more noteworthy features of 

 the excretory and circulatory systems. This latter disvision of 

 the subject may appear unnecessary owing to the extensive 

 chiton studies already published, notably those of Haller ('82), 

 Pelseneer ('99), Thiele ('02), and especially Plate ('97), but as 

 will be noted in the following pages this species differs in several 

 fundamental particulars from any other known form. 



The specimens on which Middendorff's studies were based 

 came from the shores of Kamchatka and from that locality this 

 species extends to the southward fully 2,500 miles, the southern 

 limit being approximately Monterey Bay, California. Through- 

 out the greater part of their range, as I know from personal 

 observation, they are confined to the littoral zone, rarely extend- 

 ing into water more than three fathoms in depth. Usually they 

 are more or less concealed among the red algse (especially 

 Gigartina exasperatd) upon which they feed and with which they 

 harmonize so closely that they escape the untrained eye. While 

 the largest northern specimens in my possession measure less 

 than 20 cm. (8 inches) in length, some in the vicinity of San 

 Francisco not infrequently are 25 cm. (10 inches) long. The 

 largest specimen I have ever seen measured slightly more than 



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