This question is asking us to determine what the presence of RNA but no DNA in some viruses indicates. Let`s dissect each of the options to understand them better.

Option 1: These viruses cannot replicate. This option is incorrect because viruses with RNA can still replicate using a process called RNA replication.

Option 2: These viruses have no heritable information. This option is correct. DNA is the main carrier of hereditary information, so the absence of DNA suggests that these viruses lack the ability to pass on genetic information.

Option 3: RNA transmits the hereditary information in these viruses. This option is incorrect. While RNA can carry genetic information, in this case, the absence of DNA suggests that RNA is not responsible for transmitting hereditary information.

Option 4: Their nucleic acids can be crystallized. This option is irrelevant to the question and does not provide any indication about the presence of RNA but no DNA in these viruses.

Therefore, the correct answer is option 2, which states that these viruses have no heritable information.