ODD SEA-CUCUMBERS. 



THE HOLOTHUROIDEA. 



It was my good fortune to study sea- 

 life under a scientist famous in this 

 branch of zoology, and among our stud- 

 ies was that of Holothurians or Sea- 

 cucumbers. I had learned something of 

 the odd creatures in the laboratory from 

 prepared specimens, but had not seen a 

 living animal until a day in late April 



when Professor K took a number 



of us for a biological picnic. 



We went to an exceedingly rocky 

 beach, where the stones — well carpeted 

 with sea weeds and incrusted by barna- 

 cles — were in many places surrounded 

 by tiny pools of water that had been 

 left by the receding tide. And it was 

 here that we found deep orange colored 

 Sea-cucumbers. Their bodies were part- 

 ly concealed in the wet sand, while their 

 long necks and tentacle-wreathed heads 

 were conspicuously exposed. When we 

 touched one of them, however, it seemed 

 literally to swallow itself. It turned its 

 exposed members outside in, and head 

 first down into the cavity of its body, 

 and then it withdrew so far within its 

 burrow that it was difficult to excavate 

 it, so we called a boy with a spade to 

 our assistance. 



When the Holothurians were at 

 length unearthed, we found that some 

 did resemble the garden cucumber, while 

 others had the form of a long-necked 

 squash. The body of the animal was 

 soft — it had neither skeleton nor shell — 

 and it bent easily if not contracted by 

 five powerful longitudinal muscles. 

 When these were tense, however, the 

 specimen became rigid, and the tough, 

 leathery skin much wrinkled. Several 

 Sea-cucumbers, which I placed in a pail 

 of salt water began, after a time, to 

 slowly protrude their engulfed portions, 

 and at length each long, curved neck, 

 with its circular head and waving tenta- 

 cles, was fully exposed. These tenta- 



cles, the organs of touch and smell, were 

 branched; they were arranged in five 

 groups, and their movements were con- 

 trolled by an internal water system. 



The feet of this species follow the five 

 longitudinal muscles, and they are ex- 

 tended and withdrawn by means of this 

 same water system. 



I had read that a Cucumber will vomit 

 forth a portion of its organs when it is 

 angered or frightened, and that it will 

 then live with no apparent inconve- 

 nience, while the discarded members are 

 being renewed. None of my aquatic 

 prisoners could be induced to perform 

 thus ; instead, each and every one would 

 withdraw into itself when disturbed. 



After we returned to the laboratory, 

 the Professor showed us under the 

 microscope, a bit of cuticle taken from 

 a specimen, and we saw the minute, 

 beautifully chiseled, calcareous plates or 

 spicules distributed over its surface. 

 These vary in pattern according to the 

 species upon which they incrustate. Spi- 

 cules are found in early geological rocks, 

 and hence Holothurians must have ex- 

 isted long before man's time upon the 

 earth. 



The animals have no weapons of 

 defense, but in some cases they escape 

 detection by means of protective color- 

 ation. All have well developed digestive 

 systems, and, like the earthworm, they 

 eat debris and mud. Their reproduction 

 is similar to that of other members of 

 the Echinodermata. The genital aper- 

 ture is near the tentacles, and here in 

 the female the ova are exuded, and in 

 the male the sperms. The eggs hatch 

 into minute, free swimming auricularia, 

 which are usually left to shift for them- 

 selves. The species Cucumaria laevi- 

 gata, however, protects its young. It 

 docs this by gathering them into grooves 

 on the sides of its body ; the offspring of 



